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CHAPTER 175: Central Nervous System Procedures and Devices 1179 vancomycin, 15 to 20 milligrams/kg IV loading dose, to cover methicillin-resistant S. aureus along with an antipseudomonal β-lactam such as ceftazidime, 2 grams IV every 8 hours, cefepime, 2 grams IV every 8 hours, or meropenem, 2 grams IV every 8 hours. 39,50 Once cultures return, an infectious disease consult may be helpful to determine longterm antibiotic choice and duration. Admit patients diagnosed with spinal epidural abscess for spinal surgery. If the patient will receive conservative therapy, admit to the intensive care unit for close monitoring, neurologic checks, and further management in conjunction with the spinal surgery team. REFERENCES The complete reference list is available online at www.TintinalliEM.com. Central Nervous System Procedures and Devices Jay G. Ladde LUMBAR PUNCTURE Lumbar puncture is considered the gold standard diagnostic procedure to assist clinicians with the evaluation of subarachnoid hemorrhage, meningitis, encephalitis, and other neurologic conditions. Anxiolytics, such as benzodiazepines, may be administered to improve patient comfort, relaxation, and cooperation. Contraindications to lumbar puncture are listed in Table 175-1. If an anxiolytic is used, administer a short-acting agent to avoid clouding subsequent clinical assessment. Antiseptic technique should be strictly observed. Scrub the site with a disinfecting agent and allow to dry thoroughly to avoid introduction of the chemical and the subse quent production of chemical arachnoiditis. In adults, a transverse line drawn between the iliac crests crosses the spine at the L4 spinous process. The L4-L5 interspace is the most com monly used interspace for lumbar puncture, although one can also select the L3-L4 interspace. Palpate the L4-L5 interspace while the patient is curled as tightly as possible in a fetal position. Alternatively, the patient may be seated on the edge of a bed or cart leaning over a tray stand. This latter technique is particularly useful when landmarks are uncertain due to body habitus. Use a 3 1/2-inch atraumatic 22-gauge needle in adults. Use of a needle larger than 20 gauge may double the incidence of post–lumbar puncture headache compared with a smaller needle. The use of an atraumatic or pencil-point needle (such as a Whitacre or Sprotte needle) is associated with fewer post–lumbar puncture headaches than a conventional cutting CHAPTER TABLE 175-1 Contraindications to Lumbar Puncture •   Skin infection near the site of lumbar puncture •   CNS lesion causing increased intracranial pressure, or spinal mass •   Platelet count <20,000 mm3 is an absolute contraindication; platelet counts >50,000 mm3 are safe for lumbar puncture* •   International normalized ratio ≥1.5* •   Administration of unfiltrated heparin or low-molecular-weight heparin in past 24 h* •   Hemophilia, von Willebrand’s disease, other coagulopathies* •   Trauma to lumbar vertebrae *Correct clotting factor and/or platelet levels before lumbar puncture. needle1,2 (Figure 175-1). Also, a smaller needle size using the stylet is associated with reduced frequency of post–lumbar puncture headaches.1  TECHNIQUE Assemble all equipment. Then properly position the patient and iden tify the patient’s L4-L5 interspace. Now put on sterile gown, mask, and gloves. Next, apply povidone-iodine to the area and let it dry. Apply sterile drapes.

he stylet is associated with reduced frequency of post–lumbar puncture headaches.1  TECHNIQUE Assemble all equipment. Then properly position the patient and iden tify the patient’s L4-L5 interspace. Now put on sterile gown, mask, and gloves. Next, apply povidone-iodine to the area and let it dry. Apply sterile drapes. Anesthetize the skin with 1% lidocaine by raising a skin bleb, then directing the needle toward the umbilicus, and injecting the anes thetic in a fan-shaped area around the proposed lumbar puncture site. Make sure to pull back on the plunger to check for blood return before injecting to avoid intravascular injection. Recheck the patient’s posi tion, making sure the patient is perpendicular to the horizontal and not slanted. Check the needle and make sure that it is the correct size and that the stylet is easily removed and reinserted. Identify that the needle bevel (Quincke needle) or notch (Whitacre needle) is facing the ceiling. Put together the manometer, making sure you know how the stopcocks work. Assuming you are right-handed, identify the interspinous space with your left hand and position the needle at the L4-L5 interspace, parallel to the horizontal, and direct it firmly and slowly toward the patient’s umbilicus. As the needle advances, you may feel a slight “pop, ” indicating that you have pierced the ligamentum flavum and dura mater. Remove the stylet, note draining cerebrospinal fluid (CSF), and attach the manometer to measure the opening pressure. After collecting at least 1 mL in each of four tubes, disconnect the manometer and replace the stylet before withdrawing the spinal needle ( Figure 175-2). Do not aspirate because slight negative pressure may facilitate herniation. (See Videos: Lumbar Puncture Decubitus Position; Lumbar Puncture with Ultrasound; and Lumbar Puncture Sitting Position.) If unable to penetrate the subarachnoid space, it is best to withdraw the needle completely out of the skin, and direct the needle again. In some patients (e.g., those who are extremely obese, have scoliosis, or have degenerative disease of the spine), it is particularly difficult to suc cessfully perform a lumbar puncture. US imaging of the interspinous processes is superior to palpation with regard to fewer failed attempts. 3 A 5- to 10-MHz linear probe is applied in the sagittal plane to identify the dorsal spinous processes, and the midline is then marked with a sterile marking pen. Lumbar puncture is then performed as outlined above. If attempts fail, consultation for lumbar puncture with fluoroscopic guidance may be necessary. Measure the opening pressure with the patient lying extended on his or her side. Pressures measured with the patient still curled in extreme flexion or sitting may be artificially elevated. Normal pressure FIGURE 175-1. Two types of needle for lumbar puncture. The Quincke is a bevel-type needle, and the Whitacre is a pencil-point needle. Tintinalli_Sec14_p1101-1186.indd 1179 8/2/19 12:09 PM

r side. Pressures measured with the patient still curled in extreme flexion or sitting may be artificially elevated. Normal pressure FIGURE 175-1. Two types of needle for lumbar puncture. The Quincke is a bevel-type needle, and the Whitacre is a pencil-point needle. Tintinalli_Sec14_p1101-1186.indd 1179 8/2/19 12:09 PM 1180 SECTION 14: Neurology is <170 mm H 2O. Careful repositioning (straightening the curled patient or helping the seated patient to a lying position on his or her side) can be safely performed with the needle in place. Obtain accurate pressure readings only when the patient is in a calm state if possible. Shouting, crying, or coughing can elevate the pressure falsely. Obtain four tubes, each containing at least 1 mL of CSF . Obtain red and white blood cell counts with differential for tubes 1 and 4. Tube 4 may also be used for culture and Gram staining. Tube 2 is sent for determination of protein and glucose levels. Save tube 3 for other stud ies that may be required. Table 175-2 lists normal CSF findings. See Chapters 166, “Spontaneous Subarachnoid and Intracerebral Hemor rhage, ” and 174, “Central Nervous System and Spinal Infections, ” for further discussion of CSF interpretation. FIGURE 175-2. Anatomy of the lumbar spinal interspaces for lumbar puncture. TABLE 175-2 Normal Cerebrospinal Fluid Values Parameter Value Opening pressure 50–170 mm H 2O Appearance Clear (can be clear with up to 400 cells/mm 3) Xanthochromia None Red blood cells ≤5/mm 3 WBCs ≤5/mm 3 (no polymorphonuclear leukocytes) Glucose level >40 milligrams/dL or 60%–70% of serum glucose level Protein level <50 milligrams/dL Gram stain and culture results Negative  COMPLICATIONS OF LUMBAR PUNCTURE Local discomfort is to be expected; radicular pain indicates that the needle is too lateral, which necessitates repositioning. Spinal hematoma is a particularly ominous complication. The development of severe or persistent back pain after the procedure, radicular pain, new neurologic symptoms, or sphincter disturbance indicates that a spinal hematoma may be present. Most present within the first 6 hours. 1 Management includes MRI of the spine and neurosurgical consultation. In emergent situations, it may be necessary to proceed with lumbar puncture even in patients who are anticoagulated with one or more medications. Assess platelet counts and review anticoagulation history. The decision process should take into account the risk of bleeding, thrombosis if anticoagulants are reversed, the benefit of lumbar puncture, and any alternative strategies. Antiplatelet drugs, such as aspirin and clopidogrel, offer such a low added risk to an emergent procedure that it is recommended to proceed without delay. 4,5 IV heparin has a short half-life, thus allowing for discontinuation for 4 hours prior to the procedure. 5 Warfarin may be reversed if the risk of thrombosis from reversal is low, to an international normalized ratio of less than 1.5.5 The novel oral anticoagulants have not been studied well in this scenario, but carefully consider risks and benefits before proceeding. Post–lumbar puncture headache is the most common complication of lumbar puncture. The cause is thought to be continuous CSF leakage from the dural puncture site. Traction on bridging vessels, dura, and nerves causes headache. Post–lumbar puncture headache usually begins 24 to 48 hours after the procedure and is located in the frontal or occipital area. It is pressure-like and throbbing, with variable intensity. It is intensified when the patient is sitting or standing upright and with Valsalva maneuvers such as coughing. The headache improves or resolves when the patient is supine. It can be associated with nausea, vomiting, and even vertigo and tinnitus.

pital area. It is pressure-like and throbbing, with variable intensity. It is intensified when the patient is sitting or standing upright and with Valsalva maneuvers such as coughing. The headache improves or resolves when the patient is supine. It can be associated with nausea, vomiting, and even vertigo and tinnitus. Risk factors for post–lumbar puncture headache include use of a large needle size (>22 gauge), use of a cutting (Quincke) needle, multiple attempts, and failure to replace the stylet when withdrawing the needle. 1,2 Post–lumbar puncture headache does not seem to be related to the opening pressure, the volume of CSF removed, or bed rest after the procedure. Postprocedural bed rest does not prevent this complication. 6 Diagnosis is clinical. Most headaches resolve with rest in the supine position, maintenance of hydration, and administration of antiemetics and analgesics. 1 IV caffeine (500 milligrams IV of caffeine sodium benzoate) is commonly administered, but whether or not it improves headache is controversial. 7 Persistent headache (>24 hours) can be treated with an epidural blood patch. In this procedure, usually performed by an anesthesiologist, a needle is introduced into the epi dural space, and 20 to 30 mL of the patient’s blood is injected into the epidural space. CEREBROSPINAL FLUID SHUNTS Mechanical shunting is the primary treatment for hydrocephalus. Placement of a CSF shunt is the most common pediatric neurosurgical procedure performed in the United States ( Figure 175-3). It is also the neurosurgical procedure with the highest incidence of postoperative complications. 8 Many types of CSF shunt systems exist. Most systems consist of three components, beginning with a silastic tube passed into the ventricle via a burr hole. This tubing is tunneled subcutaneously to a valve chamber. The valve chamber, the second component, establishes a pressure gradient that ensures drainage of fluid away from the ventricle. The valve chamber, or in some cases a separate reservoir, allows access to the shunt system for patency testing, pressure measurement, CSF sam pling, medication injection (e.g., chemotherapy, antibiotics), or contrast administration. Distal tubing, which is the third component, connects the valve chamber to a drainage point. The most common drainage site is the peritoneal cavity. Other drainage sites include the right atrium, gallbladder, pleural cavity, and ureter. Programmable shunt valves allow for easier control of flow rates, which is particularly useful in previously difficult cases that required frequent adjustments. The valve can be adjusted and tested using a locator and indicator tool to determine the pressure programmed into the valve. An adjustment tool can then be used to increase or decrease the valve’s Tintinalli_Sec14_p1101-1186.indd 1180 8/2/19 12:09 PM

ful in previously difficult cases that required frequent adjustments. The valve can be adjusted and tested using a locator and indicator tool to determine the pressure programmed into the valve. An adjustment tool can then be used to increase or decrease the valve’s Tintinalli_Sec14_p1101-1186.indd 1180 8/2/19 12:09 PM CHAPTER 175: Central Nervous System Procedures and Devices 1181 pressure or performance as needed. Typical nonadjustable pressure-type valves are available with low, medium, and high settings. These valves open at a pressure gradient of 2 to 4, 4 to 6, and 8 to 10 cm H 2O for the low, medium, and high settings, respectively. The adjustable valves typically have five preset pressure settings that can be selected or adjusted as clinically warranted. The patient (or family) should have been given a card that documents initial settings and any subsequent adjustments. Pressure setting can also be confirmed by radiography using the radiopaque dials on the valve. Exposure to strong magnetic fields and some MRI units can change the valve pressure setting, so all patients should have the setting verified after any exposure to strong magnetic fields. Controversy still exists as to whether programmable valves offer an advantage over traditional valves in reducing the number of revisions and extending shunt life. 9-11  CSF SHUNT MALFUNCTION Shunt malfunctions are the most common complications encoun tered with CSF shunts. Shunt malfunction can be due to obstruction, mechanical failure, overdrainage, loculation of ventricles, or abdominal complications. Obstruction Obstruction is the most common type of shunt malfunc tion. The most frequent location of obstruction is the proximal tubing, followed by the distal tubing, and then the valve chamber. Proximal obstructions usually occur within the first years after shunt insertion. Table 175-3 lists the common causes of CSF shunt obstruction. Distal obstruction is the most frequently encountered obstruction in shunts in place for >2 years. 8 Shunt obstruction usually manifests with signs and symptoms of increased intracranial pressure. Infants generally present with vomiting, irritability, and a bulging fontanelle. 12 Older children and adults may present with cephalgia, nausea, vomiting, lethargy, ataxia, and cranial nerve palsies. Mechanical Failure Mechanical failure of shunts can be secondary to fracture, disconnection, migration, or misplacement. Typically, fractures appear in distal tubing many years after shunt placement; this is due to both degradation of tubing and stress from the growth of the patient. The most common location for a fracture is along the clavicle or lower ribs. 13 Patients present with mild symptoms of increased intracranial pressure. Local symptoms of pain, mild erythema, and edema over the affected area are not uncommon. In fact, it not unusual for a fracture to be found incidentally because the shunt tract often serves as a conduit between the fractured segments. 8 Disconnection often occurs shortly after insertion and manifests as increased intracranial pressure and fluid at the skin site around the disconnection. Migration occurs when a properly placed catheter migrates to a position in which drainage is compromised partially or completely. Misplacement entails the place ment of the catheter into brain parenchyma, the choroid plexus, or the temporal horns; it usually manifests postoperatively with evidence of failure. Overdrainage Overdrainage and the slit ventricle syndrome are seen in approximately 10% of patients with shunts. 8 Because of overdrainage, the tissues actually occlude the orifices of the proximal shunt apparatus. As intracranial pressure increases, the same occluding tissue is disengaged, which allows drainage to resume.

drainage Overdrainage and the slit ventricle syndrome are seen in approximately 10% of patients with shunts. 8 Because of overdrainage, the tissues actually occlude the orifices of the proximal shunt apparatus. As intracranial pressure increases, the same occluding tissue is disengaged, which allows drainage to resume. This phenomenon is cyclical and is responsible for the episodic or waxing and waning aspect of the presenting complaint. Patients present with episodes of elevated intracranial pressure caused by a transient obstruction of the ventricular catheter from a collapsed ventricle. Decreased cerebral compliance may prevent the ventricles from fully expanding as intracranial pressure and volume increase, which further contributes to ventricular collapse. Antisiphon devices, antigravitational valves, and programmable shunt valves are devices used to reduce overdrainage; more recently, lumboperitoneal shunts have shown promise in reducing the rate of this complication. 8,14 Loculation Separate, noncommunicating CSF accumulations may develop within a ventricle so that the shunt device is not able to drain the entire ventricular system, leaving behind enlarging pockets of fluid that may have compressive sequelae. Trapped fourth ventricle syndrome occurs when the fourth ventricle becomes loculated, presumably from closure of the sylvian aqueduct. 11 Patients present with typical symptoms of increased intracranial pressure as well as symptoms of brainstem compression, including poor feeding, disconjugate gaze, and difficulty swallowing. Abdominal Complications Several abdominal processes can second arily result in shunt malfunction. Any increase in abdominal pressures, even when caused by constipation, can increase effective resistance to CSF flow. 8 The most commonly encountered serious complication is malfunction due to pseudocyst formation. Pseudocysts are localized abdominal fluid collections that form around the peritoneal catheter. Infection is the major cause. 8 They often are asymptomatic until they enlarge substantially enough to cause abdominal pain.  CLINICAL PRESENTATION Symptoms of CSF shunt malfunction usually develop over several days, although rapid deterioration within 24 hours has been reported. Clinical features include mental status changes, headache, nausea, vomiting, abdominal pain, lethargy, decreased intellectual performance, ataxia, coma, and autonomic instability. Often, the presenting complaint is vague. No single sign or symptom is accurate in predicting shunt Ventricular catheter Valve Distal tubing FIGURE 175-3. Ventriculoperitoneal shunt system. TABLE 175-3 Causes of CSF Shunt Obstruction Proximal obstruction •   Tissue debris •   Choroid plexus •   Clot •   Infection •   Catheter tip migration •   Localized immune response to the tubing Distal obstruction •   Kinking or disconnection of the tube •   Pseudocyst formation •   Infection Tintinalli_Sec14_p1101-1186.indd 1181 8/2/19 12:09 PM

unt Obstruction Proximal obstruction •   Tissue debris •   Choroid plexus •   Clot •   Infection •   Catheter tip migration •   Localized immune response to the tubing Distal obstruction •   Kinking or disconnection of the tube •   Pseudocyst formation •   Infection Tintinalli_Sec14_p1101-1186.indd 1181 8/2/19 12:09 PM 1182 SECTION 14: Neurology malfunction, although a decrease in level of consciousness may have the highest correlation with shunt malfunction. 13 As intracranial pressure increases, paralysis of upward gaze, dilated pupils, and papilledema may develop. Paralysis of upward gaze (or sundowning) is caused by impingement on the brainstem by the third ventricle as it engorges. Symptoms of slit ventricle syndrome are exacerbated or precipitated when the patient stands or exercises due to excessive CSF drainage and are relieved when the patient lies down or is in the Trendelenburg position.  SHUNT EVALUATION Identification of shunt type is important, although frequently difficult. Many different types exist, and appropriate assessment depends on the apparatus implanted. For example, many flow control valves have a high set resistance so that flow is quite slow but steady. Conversely, such a flow pattern might indicate obstruction in a low-resistance shunt. Evaluate shunt function by manual testing and radiologic studies. Palpation of the shunt allows the physician to locate the valve chamber. Shunt patency is evaluated somewhat differently for each type of device depending on features such as the presence of valves or dome- or cylinder-shaped reservoirs. Generally, testing follows intuitive expectations but still may prove perplexing to inexperienced clinicians. For a simple device, once the chamber is located, it is gently compressed and observed for refill. Difficulty compressing the chamber indicates distal flow obstruction, whereas slow refill, defined as refill requiring >3 seconds after compression, generally indicates a proximal obstruction. Compression is inaccurate for identifying shunt obstruction because up to 40% of obstructed shunts show normal refill during manual palpation. 14 Furthermore, positive predictive value has been found to be as low as 12% for shunt pumping. 15 In any case, further evaluation is required. A shunt series of plain radiographs includes anteroposterior and lateral radiographs of the skull and an anteroposterior view of the chest and abdomen (for ventriculoperitoneal shunts). Although plain radiography will identify kinking, migration, or disconnection of the shunt system, CT is required to evaluate ventricular size (Figures 175-4 and 175-5). FIGURE 175-4. CT may reveal a persistent hydrocephalus despite the presence of a shunt, which suggests a malfunction. Comparison CTs are helpful when available. Post shunt FIGURE 175-5. Slit ventricle syndrome often presents with waxing and waning symptoms. The CT is often helpful in distinguishing it from other causes of malfunction. Compare with previous CT scans because many patients with shunts have an abnormal baseline ventricular size. In one series using either CT or both CT and plain radiography, 24% of patients with documented shunt malfunction showed no radiologic evidence of the malfunction. Between 9% and 15% of pediatric patients will have profound altera tions in brain compliance leaving ventricular size unchanged even in profound shunt failure with high intracranial pressures. 8 Therefore, in patients with suggestive clinical features, unremarkable findings on CT and/or radiographic shunt series cannot be relied on to exclude shunt obstruction. Thus, obtain neurosurgical consultation whenever shunt malfunction is suspected.

ged even in profound shunt failure with high intracranial pressures. 8 Therefore, in patients with suggestive clinical features, unremarkable findings on CT and/or radiographic shunt series cannot be relied on to exclude shunt obstruction. Thus, obtain neurosurgical consultation whenever shunt malfunction is suspected. Perform a shunt tap to make the diagnosis of shunt malfunction, exclude infection, or alleviate life-threatening increased intracranial pressure. (See Video: Ventriculoperitoneal Shunt Aspiration.) Unless a CNS emergency exists, the shunt tap should be performed by a neuro surgeon to avoid damage to the valve apparatus. Emergency physicians should be prepared to perform a shunt tap if a neurosurgeon is unavailable or if a shunt tap is needed to control life-threatening increased intracranial pressure. To perform a shunt tap, locate and sterilely prepare the site over the valve system or reservoir of the shaved scalp. A 23-gauge needle or butterfly attached to a manometer is inserted into the reservoir. If no fluid returns or flow ceases, a proximal obstruction is likely. Measure the opening pressure while the reservoir outflow is occluded. An open ing pressure of ≥20 cm H 2O indicates a distal obstruction, whereas low pressures indicate a proximal obstruction. The normal basal intracranial pressure is 12 ± 2 cm H 2O. Flash MRI has assumed a growing role in serial examination for shunt function to obviate some of the radiation exposure associated with CT. In certain institutions, single-shot T2-weighted MRI has become the initial imaging modality of choice. With the advent and widespread use of programmable shunts, the concern over shunt failure after MRI exists. The MRI magnetic field can change the valve-pressure setting in programmable valves. Newer programmable valves do not reprogram even at a 3-T magnetic field. 11 In general, the settings of a programmable valve should be checked by the neurosurgeon after a patient undergoes MRI. Tintinalli_Sec14_p1101-1186.indd 1182 8/2/19 12:09 PM

etic field can change the valve-pressure setting in programmable valves. Newer programmable valves do not reprogram even at a 3-T magnetic field. 11 In general, the settings of a programmable valve should be checked by the neurosurgeon after a patient undergoes MRI. Tintinalli_Sec14_p1101-1186.indd 1182 8/2/19 12:09 PM CHAPTER 175: Central Nervous System Procedures and Devices 1183 TREATMENT OF SHUNT MALFUNCTION Surgical intervention is generally required in cases of shunt obstruc tion. As a temporizing measure, intracranial pressure can be lowered by standard methods of hyperventilation and osmotic diuresis (mannitol). If these measures fail and surgical intervention is not immediately available, intracranial pressure can be lowered by removing CSF via the reservoir if the malfunction is distal. To prevent choroid plexus bleeding, remove CSF slowly, and discontinue the process when intracranial pressure reaches 10 to 20 cm H 2O. Stable patients in whom obstruction is suspected require admission and neurosurgical consultation. Observe patients for any neurologic changes, abdominal complaints, or fever. SHUNT INFECTION Infection rates range between 3% and 20% per procedure.17-19 The highest infection rates are found in the very young and old, and in patients who have had multiple shunt revisions. There is a 12% to 26% recur rence rate of shunt infection. 17 Patients who develop shunt infections demonstrate impairment in intellectual development compared with those who do not develop infection. Half of all shunt infections present within the first 2 weeks of placement, 70% present within 2 months, and 80% present within 6 months of placement. Up to 10% of shunt infec tions present >1 year after surgery. CSF shunt infections can be categorized into internal and external infections. External infections involve the subcutaneous tract around the shunt, which on exam is usually tender, and there is often an associated fluid collection within the skin. An internal infection involves the shunt and the CSF contained within that shunt. Patients with CSF shunts have a higher risk of developing meningitis from typical pathogens than the general population. This increased risk may be due to disruption of the blood–brain barrier by foreign material. Shunt infections may be reduced with the use of antibiotic-impregnated catheters. The mortality is low if shunt infection is diagnosed and treated in a timely fashion. However, if ventriculitis develops, mortality is high, underscoring the need for prompt diagnosis and aggressive management.  BACTERIOLOGY CSF shunt infections are typically caused by low-virulence organisms. In adults, the most commonly cultured agent is Staphylococcus epidermidis, which accounts for nearly half of all shunt infections, followed by Staphylococcus aureus and Propionibacterium acnes. 21,22 The only change in the microbiology of shunt infections over the past decade has been the emergence of methicillin-resistant strains of Staphylococcus. 18 Gramnegative, anaerobic, and mixed infections account for approximately 5% to 10% of shunt infections. Gram-negative infections are associated with the highest mortality. Candida accounts for a small number of infections and should be considered in premature newborns, immunosuppressed patients, and patients on long-term, broad-spectrum antibiotics. It is associated with a 5.8% mortality rate.  CLINICAL FEATURES The clinical presentation varies with the virulence of the organ ism and the severity of the infection. Typically, patients present with symptoms of obstruction and meningeal symptoms, including mental status changes, headache, nausea, vomiting, neck stiffness, and irrita bility. Fever and abdominal pain may also be present. These signs are not universally noted.

ulence of the organ ism and the severity of the infection. Typically, patients present with symptoms of obstruction and meningeal symptoms, including mental status changes, headache, nausea, vomiting, neck stiffness, and irrita bility. Fever and abdominal pain may also be present. These signs are not universally noted. In fact, the finding of fever is highly variable, and meningismus may be present in only one third of patients with shunt infection. Abdominal pain may be the predominant symptom in patients with ventriculoperitoneal shunts. Swelling, erythema, and tenderness along the site of the shunt tubing are highly suggestive of external shunt infection. Shunt nephritis is a chronic complication of vascular shunts. Typi cally, patients develop a chronic bacteremia from coagulase-negative Staphylococcus leading to an immune response. The patient presents with a nephritic syndrome with fever episodes and increased urinary sediment. It is most commonly seen with ventriculoatrial shunts. Treatment of the underlying infection leads to complete resolution of the renal disorder.  DIAGNOSIS A shunt tap is required to exclude CSF shunt infection. A traditional lumbar puncture often misses CSF shunt infection and has no meaningful role in the evaluation when shunt infection is suspected. Analysis of fluid from infected CSF shunts usually reveals an elevated leukocyte count, elevated protein level, and normal glucose level. Almost one fifth of patients evaluated for shunt malfunction have positive CSF culture results despite normal results on CSF analysis. Other (non-CSF) laboratory values are rarely helpful in diagnosing CSF shunt infection. CT and plain radiographs of the shunt (shunt series) are required to exclude mechanical shunt malfunction, which often coexists with shunt infection. 22 Abdominal US or CT is indicated if an abdominal fluid col lection, pseudocyst, or abscess is suspected. In patients with ventricu loatrial shunts, blood cultures are helpful in identifying the offending organism. In most other cases, hematogenous dissemination of infection is rare, thus rendering blood cultures of limited value.  TREATMENT Patients with CSF shunt infection or suspected shunt infection require emergent neurosurgical consultation and admission. Until the infecting agent is identified, therapy with broad-spectrum antibiotics effective against typical pathogens (e.g., ceftriaxone and vancomycin) is recom mended. Rifampin has been given along with vancomycin for treatment of recurrent gram-positive infections because it easily penetrates the CSF . Early removal of the colonized device is important. HALO DEVICES The halo vest provides one of the most rigid types of cervical immobilization available. The halo vest consists of a lightweight radiolucent ring attached to a lightweight adjustable vest. Current vests allow adjust ment of the cervical spine in multiple planes. Titanium pins that do not interfere with MRI are stronger, lighter, and more expensive than older stainless steel pins. Pins are usually tightened to 8 lb of pressure (Figure 175-6). 23,24 Halo devices are indicated for stabilization of an unstable cervical spine, including stabilization of fractures, dislocations, and subluxations, and alignment of severe kyphotic and scoliotic spines.  COMPLICATIONS Pin loosening is the most common complication encountered in the ED. 23,24 Obtain neurosurgical consultation and exclude infection of the pin site. If pin loosening has caused movement of the halo device, assume that the cervical spine is unstable, immobilize the cervical spine using an alternative technique, and obtain radiographs to assess for proper alignment. Tangential plain radiography, CT, or MRI can be used to exclude penetration of a pin through the inner table of the skull.

caused movement of the halo device, assume that the cervical spine is unstable, immobilize the cervical spine using an alternative technique, and obtain radiographs to assess for proper alignment. Tangential plain radiography, CT, or MRI can be used to exclude penetration of a pin through the inner table of the skull. Pin-site infection is the second most frequently encountered complication. It occurs in approximately 10% to 20% of patients with halo devices. 24 Nearly 50% of infections occur in the first 4 weeks after halo placement, and 60% involve the anterior pins. Careful examination is required to differentiate a localized pin-site infection from less com mon, more serious infections (<1% of cases), such as cellulitis, osteomyelitis, and abscess formation. 24 Consider these more serious infections if there is persistent pain, continued drainage despite antibiotic therapy, clear drainage, or a history of a fall. Patients with cellulitis often present with fever and systemic signs and symptoms of infection. Patients with osteomyelitis usually have a prolonged infection, pin-site loosening, and radiologic abnormalities. Patients who develop an abscess usually have neurologic changes and evidence of intertable penetration (CSF leak, trauma). Tintinalli_Sec14_p1101-1186.indd 1183 8/2/19 12:09 PM

ns and symptoms of infection. Patients with osteomyelitis usually have a prolonged infection, pin-site loosening, and radiologic abnormalities. Patients who develop an abscess usually have neurologic changes and evidence of intertable penetration (CSF leak, trauma). Tintinalli_Sec14_p1101-1186.indd 1183 8/2/19 12:09 PM 1184 SECTION 14: Neurology Local pin-site infections are commonly managed with local wound care. The skin around the pin site must be pulled away to allow thorough cleaning of the skin beneath the pin and the skin–pin interface with soap and water four times a day. Obtain culture specimens from the wound site and administer antibiotics effective against skin pathogens (e.g., Staphylococcus and Streptococcus species). If local infection does not respond to treatment or if cellulitis, osteomyelitis, or abscess is sus pected, obtain neurosurgical consultation for admission, IV antibiotics, and possible surgical intervention. Pin-site discomfort occurs in up to 20% of patients. 23,24 It is most commonly a result of local inflammation. However, consider infection (localized or systemic) in each case. Sensory and motor deficits or paresthesias indicate nerve damage or pressure, whereas painful mastication indicates temporalis muscle inflammation, which often indicates too lateral a placement of pins. If infection is excluded, a short course of analgesics is recommended. Neurosurgical consultation is required if pain continues or a serious complication is suspected. Ring migration or loss of immobilization occurs in 10% to 13% of patients. Suspect loss of immobilization in patients complaining of neck pain and change in fit or position of the ring or vest. Immediately immobilize the cervical spine using an alternative technique (e.g., hard collar plus backboard) and obtain radiographs to assess for changes in alignment. Obtain neurosurgical consultation for reapplication of the halo device. Skin breakdown and pressure sores occur in 11% to 30% of patients. If either is present, inspect the vest for adequate padding and strap position. Urgent referral to a neurosurgeon for refitting may be required. Dysphagia occurs in 1% to 2% of patients with halo devices. 23-25 Immobilization that holds the head in exaggerated extension is the usual cause of the dysphagia. Halo adjustment will remedy this problem. Alternatively, dysphagia can occur following anterior displacement of a bone graft. This diagnosis can be made by plain radiography or a swal lowing study, and emergency surgical intervention is required. Dural punctures occur in 1% to 2% of patients and are a result of halo system trauma. 23-25 This is rarely attributable to postapplication trauma because newer pin tighteners are designed to fail when torque exceeds 8 lb. Symptoms include headache, malaise, or visual changes. Physical examination may reveal a CSF leak or evidence of skull fracture. All patients with dural punctures require admission and neurosurgical consultation. Treatment includes elevation of the head, IV antibiotics, and pin removal. In rare cases, CPR is required in patients with halo devices. To perform chest compressions, remove the anterior portion of the vest. Instructions for removing the halo vest are printed on the front of most vests. Intubation is performed with the halo in place. Emergent or semi-emergent intubation was required 13% of the time in one series. If orotracheal intubation is unsuccessful, other airway management options include nasotracheal intubation, laryngeal mask airway, and cricothyrotomy. SPECIAL POPULATIONS Use of halo devices carries a special risk in the elderly patient.

. Emergent or semi-emergent intubation was required 13% of the time in one series. If orotracheal intubation is unsuccessful, other airway management options include nasotracheal intubation, laryngeal mask airway, and cricothyrotomy. SPECIAL POPULATIONS Use of halo devices carries a special risk in the elderly patient. A mortality rate of 21% is reported in patients >79 years of age.25 Rates of serious complications, such as respiratory depression (8% of cases) and dysphagia (11% of cases), are much higher in elderly patients. OTHER CENTRAL NERVOUS SYSTEM DEVICES  INTRATHECAL BACLOFEN INFUSION DEVICES Generalized dystonia occurs in 15% to 25% of patients with cerebral palsy. Baclofen, a γ-aminobutyric acid agonist that acts at the level of the spinal cord by impeding the release of excitatory neurotransmit ters, decreases spasticity. Oral baclofen offers patients only mild relief because of its inability to cross the blood–brain barrier and its poor lipid solubility. Intrathecal administration (Figure 175-7) is more effective, requires lower dosages, and leads to higher CSF levels. Intrathecal baclofen reduces spasticity and improves gait, sitting ability, and upper extremity function in most patients. 26 Intrathecal baclofen pumps are also used to treat spasticity related to spinal cord injury, multiple scle rosis, brain injury, cerebrovascular accidents, and perinatal infection sequelae. 26,27 Complications observed in patients receiving continuous intrathecal baclofen can be divided into medication-related, mechanical, and infection-related complications and are listed in Table 175-4. When a complication occurs disrupting the administration of baclofen, withdrawal symptoms can be severe and life threatening, including extreme hypertonicity and spasms that may lead to rhabdomyolysis. The apparent accelerated spasticity should signal to the provider that a potential complication has arisen. Oral baclofen, dantrolene, and oral or parenteral benzodiazepines may be used to alleviate these symptoms. Infectious complications occur more frequently in children, revised pumps, and those placed subcutaneously. 27,28 Infection rate is 10%, with most infections presenting during the first month after placement. 27 Most infections are caused by Staphylococcus species, with a recent increase in methicillin-resistant S. aureus.27 Serious infections and meningitis may arise even without local symptoms. The major ity of infections require neurosurgical consultation and IV/intrathecal FIGURE 175-6. Demonstration of halo device application by emergency medical technicians at a high school assembly. [Reproduced with permission from North Carolina SAFETeens, Inc.] FIGURE 175-7. Typical baclofen pump. Tintinalli_Sec14_p1101-1186.indd 1184 8/2/19 12:09 PM

ire neurosurgical consultation and IV/intrathecal FIGURE 175-6. Demonstration of halo device application by emergency medical technicians at a high school assembly. [Reproduced with permission from North Carolina SAFETeens, Inc.] FIGURE 175-7. Typical baclofen pump. Tintinalli_Sec14_p1101-1186.indd 1184 8/2/19 12:09 PM CHAPTER 175: Central Nervous System Procedures and Devices 1185 antibiotics. Direct concerns about baclofen pumps to the neurosurgeon, or other specialists who are expert in programming the pump.  IMPLANTABLE CENTRAL NERVOUS SYSTEM STIMULATORS The pathogenesis of Parkinson’s disease is thought to involve unregu lated activity of the subthalamic nucleus and globus pallidus interna. High-frequency stimulation with implantable CNS devices is being used for suppression of parkinsonian and essential tremors. Neuro stimulation is typically used if drug therapy has failed to control tremors. Neurostimulation is as efficient at controlling tremors as classic thalamotomy but is less invasive. Deep brain stimulation studies have shown a 40% to 75% improvement in motor scores as well as improve ment of rigidity, bradykinesia, and postural instability. 29 Reported complication rates range from 7% to 65%, with a decline in the number of reported complications as physician experience increases. 29 Infection rates approach 3% to 10%. 29 Patients may present to the ED with var ied complaints, including problems related to the subcutaneous pulse generator, temporary or permanent paresthesias, dysarthria, disequilibrium, or failure of the neurostimulator to suppress tremors. Neurosurgical consultation is needed because these complaints may represent lead displacement or migration requiring surgical correction or replacement. If the diagnosis remains uncertain, observation with the stimulator in the off position may be required to help differentiate mechanical failure from an acute neurologic deficit.  SPINAL CORD STIMULATION Spinal cord stimulation is an established modality for treating chronic back pain, multiple sclerosis pain, complex regional pain syndromes, phantom pain, diabetic neuropathy, postherpetic neuralgia, angina pectoris, intractable pain associated with some malignancies, and the pain syndromes associated with vascular disease. Multicontact electrodes are placed in the epidural space, and the distal end of the electrode is con nected to an internalized pulse generator. The therapeutic response is thought to be a result of stimulation of one of several dorsal tracts as well as activating the release of inhibitory neurotransmitters. 30,31 Complications include dural puncture, spinal cord compression, CSF leak, hemorrhage, infection, abscess, epidural fibrosis, migration, interruption of wires, corrosion of contacts, and battery failure. The most frequent complication is device failure, accounting for 17% to 25% of complica tions. 32 The rate of infection is reported between 2.5% and 5%.31 Patients with these devices should not undergo MRI.  PERIPHERAL NERVE STIMULATION Peripheral nerve stimulators are used to treat neuropathic pain disorders in patients with chronic intractable pain such as with occipital neural gia. The device is similar to other stimulators except that the electrodes are placed in the subcutaneous tissue overlying the peripheral nerves. Case reports of interference of stimulators causing pauses in cardiac pacemakers exist and thus must be considered in patients with both a pacemaker and stimulator and a new conduction abnormality. REFERENCES The complete reference list is available online at www.TintinalliEM.com.

issue overlying the peripheral nerves. Case reports of interference of stimulators causing pauses in cardiac pacemakers exist and thus must be considered in patients with both a pacemaker and stimulator and a new conduction abnormality. REFERENCES The complete reference list is available online at www.TintinalliEM.com. TABLE 175-4 Complications of Intrathecal Baclofen Infusion Medication related •   Hypotension •   Bradycardia •   Apnea •   Oversedation •   Respiratory depression Mechanical •   Pump pocket effusions •   Pump failure •   Catheter extrusion •   Catheter dislodgement Infection •   Local infection •   Meningitis •   Cerebrospinal fluid fistula formation Tintinalli_Sec14_p1101-1186.indd 1185 8/2/19 12:09 PM Tintinalli_Sec14_p1101-1186.indd 1186 8/2/19 12:09 PM This page intentionally left blank