Browse the corpus

1142 SECTION 14: Neurology patients, but liberal use of CT scanning is encouraged because excep tions to the tentative clinical diagnosis are frequent.29 Address airway, breathing, and circulation immediately. Consider reversible causes of coma, such as hypoglycemia or opiate overdose. Access all available historical sources (EMS personnel, caregivers, fam ily, witnesses, medical records, etc.) to aid in diagnosis. The tempo of onset of the coma is of great diagnostic value. Abrupt coma suggests abrupt CNS failure with possible causes such as catastrophic stroke or seizures. A slowly progressive onset of coma may suggest a progressive CNS lesion such as tumor or subdural hematoma. Metabolic causes, such as hyperglycemia, may also develop over several days. Address general examination and measurement of vital signs (including oxygen saturation and temperature) following stabilization and resuscitation. General examination may reveal signs of trauma or suggest other diagnostic possibilities for the unresponsiveness. For example, a toxidrome may be present that suggests diagnosis and treatment, such as the opiate syndrome with hypoventilation and small pupils. Neurologic testing deviates from the standard examination. Fine tests of weakness, such as testing for pronator drift of the outstretched upper extremities, are not possible in the unresponsive patient. However, asymmetric findings on examination of cranial nerves through pupillary examination, assessment of corneal reflexes, and testing of oculovestibular reflexes may suggest focal CNS lesions. Abnormal extensor or flexor postures are nonspecific for localization or cause of coma but suggest profound CNS dysfunction. Asymmetric muscle tone or reflexes raise the suspicion of a focal lesion. The goal of the physician is to rapidly determine if the CNS dysfunction is from diffuse impairment of the brain or if signs point to a focal (and perhaps surgically treatable) region of CNS dysfunction. CT is the neuroimaging procedure of choice. Acute hemorrhage is readily identified, as is midline shift and mass lesions. Consider lumbar puncture if CT scan findings are unremarkable and subarachnoid hemorrhage or CNS infection is suspected. Suspect basilar artery thrombosis in a comatose patient with “normal” results on head CT, in which the only finding may be a hyperdense basilar artery. 30 MRI or cerebral angiography is needed to make the diagnosis of basilar artery thrombosis.  SPECIAL CONSIDERATIONS IN COMA If trauma is suspected, maintain stabilization of the cervical spine during assessment. If protection of the airway is in doubt or the coma state is likely prolonged, then protect the airway by intubating the patient. Rapidsequence intubation techniques are discussed at length in Chapter 29A, “Tracheal Intubation” and Chapter 29B, “Mechanical Ventilation. ” For children, consider ingestions, infections, and child abuse in the appropriate clinical setting. Patients who have had generalized seizures and remain unresponsive may be in a continuing state of electrical seizures without correspond ing motor movements. This is called nonconvulsive status epilepticus or subtle status epilepticus and can be described as electromechanical dissociation of the brain and body. If the motor activity of the seizure stops and the patient does not awaken within 30 minutes, then con sider nonconvulsive status epilepticus. Obtain neurologic consultation and electroencephalography.

epilepticus or subtle status epilepticus and can be described as electromechanical dissociation of the brain and body. If the motor activity of the seizure stops and the patient does not awaken within 30 minutes, then con sider nonconvulsive status epilepticus. Obtain neurologic consultation and electroencephalography.  TREATMENT Treatment of coma involves identification of the cause of the brain failure and initiation of specific therapy directed at the underlying cause. Attend to airway, ventilation, and circulation. Evaluate and treat for readily reversible causes of coma, such as hypoglycemia and opioid toxicity. Antidotes Rapid point-of-care glucose determination can identify the need for dextrose. Although thiamine should be administered before glucose infusion in patients with a suspected history of alcohol abuse or malnutrition, thiamine is not necessary for all patients. Routine use of flumazenil in coma of unknown cause is not recommended. 31 Naloxone, an opiate antagonist, may be useful in diagnosis and treatment of coma of unknown cause, given that the miosis of the opiate toxidrome can be absent with some opioids and mixed ingestions. Increased Intracranial Pressure If history, physical examination, or neuroimaging findings suggest increased ICP , specific steps can reduce or ameliorate any further rise in ICP . Any noxious stimulus, including “bucking” the ventilator, can increase ICP , so use paralytic and sedative agents. A general recommendation is to keep the head elevated about 30 degrees and at midline to aid in venous drainage. Mannitol (0.5 to 1.0 gram/kg IV) can decrease intravascular volume and brain water and may transiently reduce ICP . Hypertonic saline infusion has also been found to be effective in reducing ICP . In cases of brain edema associ ated with tumor, dexamethasone, 10 milligrams IV , reduces edema over several hours. Hyperventilation with reduction of partial pres sure of arterial carbon dioxide can reduce cerebral blood volume and transiently lower ICP . Current recommendations are to avoid excessive hyperventilation (partial pressure of arterial carbon dioxide ≤35 mm Hg) during the first 24 hours after brain injury. Brief hyperventilation may be necessary for refractory intracranial hypertension. Data to rec ommend specific therapy are lacking, and preferences among individu als and institutions vary greatly, so communicate early with consultants and admitting physicians.  DISPOSITION AND FOLLOW-UP Patients with readily reversible causes of coma, such as insulin-induced hypoglycemia, may be discharged if home care and follow-up care are adequate and a clear cause for the episode is suspected. Admit patients with persistent altered consciousness. Most institutions depend on emergency physicians to stabilize the patient’s condition and correctly assign a tentative diagnosis so that the patient may be admitted to the proper specialty service. If the appropriate service is not available, then consider transfer to another hospital after patient stabilization. REFERENCES The complete reference list is available online at www.TintinalliEM.com. Ataxia and Gait Disturbances J. Stephen Huff INTRODUCTION Ataxia and gait disturbances may be symptoms of many disease pro cesses and generally are not in themselves diagnoses. Ataxia is uncoordinated movement. A gait disorder is an abnormal pattern or style of walking. The presenting problem may be articulated by the patient or family as weakness, dizziness, stroke, falling, or another nonspecific chief complaint. Such symptoms must always be viewed in the context of the patient’s overall clinical picture. This chapter reviews the more common causes of acute ataxia and gait disorders (Table 169-1).

problem may be articulated by the patient or family as weakness, dizziness, stroke, falling, or another nonspecific chief complaint. Such symptoms must always be viewed in the context of the patient’s overall clinical picture. This chapter reviews the more common causes of acute ataxia and gait disorders (Table 169-1). PATHOPHYSIOLOGY Clinicians often erroneously think that ataxia and gait disorders result primarily from cerebellar lesions. However, such ataxia and gait prob lems may result from systemic conditions that affect different elements of the central or peripheral nervous systems. Cerebellar lesions may indeed cause ataxia, but isolated lesions of the cerebellum are not the most common cause of these complaints. Ataxias may be classified as either motor (cerebellar) or sensory. CHAPTER Tintinalli_Sec14_p1101-1186.indd 1142 8/2/19 12:08 PM

nt elements of the central or peripheral nervous systems. Cerebellar lesions may indeed cause ataxia, but isolated lesions of the cerebellum are not the most common cause of these complaints. Ataxias may be classified as either motor (cerebellar) or sensory. CHAPTER Tintinalli_Sec14_p1101-1186.indd 1142 8/2/19 12:08 PM CHAPTER 169: Ataxia and Gait Disturbances 1143 affecting the peripheral nerves, spinal cord, or cerebellar input tracts. Coordinated motor performance is faulty, even though motor systems and the cerebellum are intact. Sensory ataxias may be somewhat compensated by visual sensory information. Loss of visual information leads to the observation that sensory ataxias often worsen in poor lighting conditions.  GAIT DISORDERS No organized classification scheme exists for gait disorders, and differ ent authors categorize abnormal gaits in descriptive terms. A cerebellar or motor ataxic gait is wide-based with unsteady and irregular steps, and compensation for environmental barriers may be lacking. The gait of sensory ataxia resulting from loss of proprioception is notable for abrupt movement of the legs and slapping impact of the feet with each step. A variety of other terms are used to describe abnormal gaits. An apraxic gait is one in which the patient seemingly has lost the ability to initiate the process of walking, an “ignition failure. ” This may occur with right or nondominant hemispheric lesions. Frontal lobe dysfunction may result in a similar gait and may be seen in normal pressure hydrocephalus. The term festinating gait is used to describe narrowly based minia ture shuffling steps and is common in Parkinson’s disease. An abnormal gait with outward swinging or circumabduction of the leg suggests a mild hemiparesis reflecting the asymmetric weakness of the proximal lower extremity muscles. Bilateral weakness of the trunk and pelvic girdle muscles may result in a waddling gait from failure to maintain the normal position of the pelvis relative to the lower extremities. A functional gait disorder is one in which the patient is unable to walk normally, although all motor pathways, sensory pathways, and cerebellar functions may be demonstrated to be functioning normally. The underlying problem is often a conversion disorder. Functional gaits may be bizarre, at times resembling a person balancing on a tightrope and seemingly threatening to fall but not falling. A dramatic functional gait with flailing movements without falling actually demonstrates that strength, balance, and coordination are intact. A unifying concept defines gait disorders according to the level of processing of neurologic information ( Table 169-2). 6,7 The classification scheme is not ideal but does allow a thoughtful approach to patient diagnosis. Low-level gait disturbance refers to disorders of proprioception or dysfunction of the musculoskeletal system. Middle-level gait disturbance causes distortion of appropriate interaction of postural and motor pro cesses or synergies. This might include stroke with paralysis, cerebellar dysfunction, or diseases of the basal ganglia such as Parkinson’s disease.

orders of proprioception or dysfunction of the musculoskeletal system. Middle-level gait disturbance causes distortion of appropriate interaction of postural and motor pro cesses or synergies. This might include stroke with paralysis, cerebellar dysfunction, or diseases of the basal ganglia such as Parkinson’s disease. High-level gait disturbances seemingly involve structures or processes TABLE 169-1 Common Etiologies of Acute Ataxia and Gait Disturbances Systemic conditions •  Intoxications  with diminished alertness •  Ethanol •  Sedative—hypnotics •  Intoxications  with relatively preserved alertness (diminished alertness at higher levels) •  Phenytoin •  Carbamazepine •  Valproic  acid •  Heavy  metals—lead, organic mercurials •  Other  metabolic disorders •  Hyponatremia •  Inborn  errors of metabolism •  Wernicke’s  disease Disorders predominantly of the nervous system •  Conditions  affecting predominantly one region of the CNS •  Cerebellum •  Hemorrhage •  Infarction •  Degenerative  changes •  Abscess •  Cortex •  Frontal  tumor, hemorrhage, or trauma •  Hydrocephalus •  Subcortical •  Thalamic  infarction or hemorrhage •  Parkinson’s  disease •  Normal  pressure hydrocephalus •  Spinal  cord •  Cervical  spondylosis and other causes of spinal cord compression •  Posterior  column disorders •  Conditions  affecting predominantly the peripheral nervous system •  Peripheral  neuropathy •  Vestibulopathy  MOTOR ATAXIAS Motor ataxias (also referred to as cerebellar ataxias) are usually caused by disorders of the cerebellum. The sensory receptors and afferent pathways are intact, but integration of proprioceptive information is faulty. Involvement of the lateral cerebellum (one of the cerebellar hemispheres) may lead to a motor ataxia of the ipsilateral limb. Lesions affecting primarily the midline portion of the cerebellum often cause problems with axial muscle coordination, which is reflected in difficulty maintaining a steady upright standing or sitting posture. There are many reports of CNS lesions producing motor ataxia in what intuitively seem unlikely locations. Supratentorial infarctions, particularly small, deep infarctions, and lacunae of the posterior limb of the internal capsule have been reported to cause isolated hemiataxia. It is postulated that interruption of either ascending or descending cerebellar to cortical pathways are the cause of this motor-type ataxia. 1 Small infarctions or hemorrhages in thalamic nuclei may produce a clinical picture of motor- or cerebellar-like ataxia with hemisensory loss. These effects are seen contralateral to the lesion. 2 Lesions affecting the frontal lobe, such as tumors or cystic masses, may cause a motor ataxia of the contralateral extremities through poorly understood mechanisms. 3 Nontraumatic spinal cord compression may present with gait ataxia or abnormality.4  SENSORY ATAXIAS Sensory ataxias are due to failure of transmission of proprioception or position sense information to the CNS. Failure may arise from disorders TABLE 169-2 Classification of Gait Disorders Low-level gait disorders •  Musculoskeletal  problems •  Arthritic  gait or other joint or skeletal problems •  Muscle  weakness •  Peripheral  sensory problems •  Sensory  ataxic gait •  Vestibular  problems Middle-level gait disorders •  Hemiplegia •  Paraplegia •  Motor  or cerebellar ataxia •  Parkinson’s  disease •  Dystonia,  chorea, other movement disorders High-level gait disorders •  Senile  gait (cautious gait) •  Frontal  ataxic gait •  Apraxic  gait (gait ignition failure) •  Frontal  disequilibrium Tintinalli_Sec14_p1101-1186.indd 1143 8/2/19 12:08 PM

•  Paraplegia •  Motor  or cerebellar ataxia •  Parkinson’s  disease •  Dystonia,  chorea, other movement disorders High-level gait disorders •  Senile  gait (cautious gait) •  Frontal  ataxic gait •  Apraxic  gait (gait ignition failure) •  Frontal  disequilibrium Tintinalli_Sec14_p1101-1186.indd 1143 8/2/19 12:08 PM 1144 SECTION 14: Neurology that choose the appropriate responses for the support surface, body position in space, and intention of the patient. Cautious gait, apraxic gait, and the frontal gait disorder conceptually fall into this group with pathology that correlates with lesions in the frontal cortex or thalamus. This latter group is the least understood and often the source of clinical confusion. CLINICAL FEATURES  HISTORY Collect historical information about the entire symptom constellation including presence of headache, nausea, fever, weakness, or numbness. A history of fever, review of medication history, or family history of ataxia may lead to the diagnosis in individual cases. The nature of onset of symptoms and the time course of the process guide the pace of investigations. For example, abrupt onset of gait difficulty in a patient with severe headache, drowsiness, nausea, and vomiting should suggest an acute process within the CNS, possibly a hemorrhage into the cerebellum. The possible consequences of that diagnosis are severe and may require immediate attention. At the other extreme, a patient without significant medical history who is brought to the ED with a stumbling gait after an episode of binge drinking requires examination and may need nothing other than observation unless history or physical examination suggests trauma or some alternative cause for the symptoms.  PHYSICAL EXAMINATION The following discussion of the neurologic examination assumes that the gait disorder is the dominating abnormality. Physical examination including testing of cranial nerves, mental status, sensation, and the motor system is necessary and may yield findings that lead to an unanticipated diagnosis. An approach to the neurologic examination is presented in Chapter 164. General physical examination of a patient with ataxia or gait distur bance should include determination of orthostatic vital signs. Orthostatic hypotension may be present in hypovolemia, diabetic neuropathy, and other neurologic syndromes. Especially in the elderly, fluid replacement for simple hypovolemia may often correct symptoms of unsteadiness. Gait testing is one of the most important parts of the directed neuro logic examination. Observe the patient sitting upright in the stretcher, and then have the patient rise, stand, walk, and turn around. The patient should be asked to walk at a normal speed, then walk on the heels, and then the toes. Tandem gait is toe-to-toe walking and tests many elements of the nervous system. Do not assume a normal examination without observing ambulation. Cerebellar functions are tested by asking the patient to perform smooth voluntary movements and rapidly alternating movements. Dyssynergia (breakdown of movements into parts), dysmetria (inaccurate fine movements), or dysdiadochokinesia (clumsy rapid movements) may indicate a lateral cerebellar lesion. The rapid thigh-slapping test particularly examines rapidly alternating movements. This is correctly performed by asking the patient to pat the thigh with the palm then the back of the same hand in alternating fashion, making a sound with each rapid slap. The maneuver is performed with each hand in turn. The finger-to-nose test may be helpful in distinguishing between cerebellar and posterior column (proprioceptive) lesions. Performing this test with the eyes closed tests proprioception in the upper extremities.

alternating fashion, making a sound with each rapid slap. The maneuver is performed with each hand in turn. The finger-to-nose test may be helpful in distinguishing between cerebellar and posterior column (proprioceptive) lesions. Performing this test with the eyes closed tests proprioception in the upper extremities. A test for cerebellar function that emphasizes the lower extremities is the heel-toshin test. In cerebellar disease, the heel may initially overshoot the other shin or knee, and the action is done with a series of jerky movements. In posterior column disease, there may be difficulty locating the knee with the heel, and the movement down the shin typically weaves from side to side or falls off. Another test commonly used for cerebellar function is checking for abnormal rebound; with sudden release of a flexed forearm against resistance, the individual fails to check further excessive flexion. Another example of rebound phenomena is when a tapped outstretched arm excessively oscillates back and forth for several seconds. The Romberg test is primarily a test of sensation, and if positive, it may distinguish sensory from motor ataxia. While standing with arms outstretched and eyes open, observe the patient for signs of unsteadi ness. The feet should be narrowly spaced, and the posture should be easily maintained. The inability to maintain a steady standing posture (or, in extreme cases, a seated position) confirms that an ataxia is pres ent but does not yet give any information about the type of ataxia. Then ask the patient to close his or her eyes, which eliminates visually orienting information. If the ataxia worsens with the loss of visual input, then the Romberg sign is present or positive, suggesting sensory ataxia with a problem of proprioceptive input (posterior column, vestibular dysfunction) or a peripheral neuropathy. Further neurologic examina tion is indicated to confirm the suspicion of sensory ataxia. In patients who show little or no change in unsteadiness with eye closure (Romberg test–negative), a motor ataxia is suggested, with possible localization of that problem to the cerebellum. Note that many normal individuals will have some small increase in unsteadiness with eye closure. Historically, tabes dorsalis (neurosyphilis) was a common cause of sensory ataxia. In tabes dorsalis, the posterior columns and posterior spinal roots degenerate primarily in the lumbosacral region. The loss of proprioceptive information from the lower extremities renders the patient dependent on visual cues for correct gait. The classic descrip tion depicts a patient walking slowly with wide gait while staring at the ground. In darkness or with interruption of vision, the patient is unable to walk. The gait in this condition appears peculiar, with the foot first raised and then slapped to the ground with each step. These abnor malities reflect the loss of proprioceptive information from the poste rior roots and posterior columns. Consider the possibility of vitamin 12 deficiency in patients with evidence of posterior column disease. If the deficiency is left untreated, an initial unsteady gait may progress to weakness, spasticity, and ataxia. The finding of a megaloblastic anemia may be a clue, but the neuropathy may precede the anemia. Sensory examination in a patient with unsteady gait or ataxic move ments should include position or vibration testing (posterior columns), as well as testing sensation to pinprick. Testing of the deep tendon reflexes will serve largely to discover asymmetry or spasticity that might suggest an alternative diagnosis. Acute cerebellar injury may result in muscle hypotonia for a few days or weeks.

uld include position or vibration testing (posterior columns), as well as testing sensation to pinprick. Testing of the deep tendon reflexes will serve largely to discover asymmetry or spasticity that might suggest an alternative diagnosis. Acute cerebellar injury may result in muscle hypotonia for a few days or weeks. Nystagmus is seen in many different disorders due to lesions in a variety of different locations of the CNS, but the presence of nystagmus does suggest that a pathologic process is intracranial (CNS or vestibular) and not in the spinal cord or peripheral nervous system (see Chapter 170, “Vertigo”). DIAGNOSIS Assuming a primary complaint of ataxia, the first task is to determine whether the ataxia is sensory or motor, and whether the primary process is systemic or within the nervous system. If the ataxia is thought to result from problems within the nervous system, the next question is one of localization to the peripheral nervous system or the CNS and then per haps to a more specific anatomic location. Finally, the tempo of the ill ness, comorbid diseases, and other clinical findings guide investigations and may allow a disease-specific diagnosis. A patient with acute gait failure over hours to days needs thorough evaluation in the ED, often requiring neuroimaging and lumbar punc ture if cerebrospinal fluid infection is suspected. Acute ataxia or gait disturbance may also be evaluated by consultation if available, and possible admission, in contrast to a patient with gradual loss of abilities over weeks or months where outpatient referral and evaluation may be more appropriate. SPECIAL POPULATIONS  THE GERIATRIC PATIENT The gait changes with advancing age. A typical constellation includes gait slowing, shortening of the stride, and widening of the base. This results in the appearance of a guarded gait—that is, the gait of someone about to slip and fall. Many patients are aware of the loss of speed and adaptive balance and acknowledge the need to be careful. The nature of the senile gait is not fully understood but may represent a mild degree of neuronal loss, failing proprioception, slowing of corrective responses, or Tintinalli_Sec14_p1101-1186.indd 1144 8/2/19 12:08 PM