Dr. Huntley's
Diagnosis
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Anne Cather Cutlip
Coma represents a state of unarousable unresponsiveness in which the patient has no evidence of self or environmental awareness (1).
A patient presenting with coma should be considered a medical emergency.
A. Etiologic categories. Consider these categories when evaluating a comatose patient.
1. Traumatic: contusion, intracerebral hemorrhage, diffuse axonal injury.
2. Metabolic: diabetes; thyroid disease; acid-base or electrolyte abnormalities; hypoxia; hepatic, renal, or adrenal abnormalities; hypo- or hyperthermia.
3. Vascular: cerebrovascular accident, subarachnoid hemorrhage, aneurysm, hypertensive encephalopathy, eclampsia.
4. Infectious: meningitis, abscess, subdural empyema, encephalitis.
5. Toxic: poisoning, overdose, withdrawal syndromes.
6. Structural: tumor.
7. Psychogenic: conversion reaction, depression, catatonia, malingering.
B. Focal versus nonfocal. The presentation of coma is typically focal or nonfocal.
1. Focal: intracerebral hemorrhage, ischemic stroke, demyelinating diseases.
2. Nonfocal: vascular, toxic, metabolic conditions, nutritional deficiencies, seizures, psychiatric conditions.
3. Either: trauma, infections, tumors (2).
A. Characteristics. Coma patients essentially behave in a reflex manner without spontaneous or purposeful movements, language cognizance or expression, or specific localizing responses (3).
B. Confounding conditions include some medications, mechanical ventilation, immobilized extremities, facial edema, and diurnal variations.
C. Differential diagnosis. Less severe conditions of altered consciousness include vegetative state, the minimally conscious state, akinetic autism, and locked-in syndrome (3).
A. General examination. A thorough general examination, including vital signs, helps to establish and rule out potential causes of coma. Look for evidence of head trauma or metabolic encephalopathy.
B. Neurologic examination. A detailed neurologic examination, including mental status; motor, sensory, reflex coordination; gait; and cranial nerve testing, will help distinguish the location and degree of dysfunction. Look for the following important features:
1. Level of consciousness. Is the patient responsive at all? To what degree?
2. Brainstem function
a. Pupils: assess cranial nerves (CN) 2 and 3 for anisocoria, miosis, pinpoint, mydriasis, or fixed, midposition pupils.
b. Eye movements: assess conjugate gaze, gaze deviation, nystagmus, and spontaneous movements (CN 3, 4, and 6).
c. Funduscopic examination: assess for papilledema and underlying diseases. Corneal reflexes (CN 5 and 7); gag and cough reflexes (CN 9 and 10).
3. Breathing patterns. Cheyne-Stokes respiration suggests cerebral hemispheric or diencephalic injury or an encephalopathy (hypoxic or metabolic). Central hyperventilation suggests brainstem injury. Ataxic or Biot’s respiration, which can progress to apnea, suggests injury to the reticular formation in the medulla and pons.
4. Sensorimotor activity. Are there spontaneous, volitional movements? Is there other motor activity such as choreoathetosis, decerebrate or decorticate activity, myoclonus, asterixis, or seizure activity? Is the muscle tone flaccid, rigid, spastic, or clonic? Is the response to painful stimuli purposeful, flexion withdraw, abnormal posturing, or no response at all?
5. Tendon reflexes. Are the reflexes asymmetric, increased, or decreased?
6. Glasgow Coma scale. Measures the depth and duration of altered consciousness based on the best response to three actions: eye opening, verbal response, and motor response to commands or painful stimulus.
A. Clinical laboratory tests. Complete chemistry profile (including electrolytes, glucose, calcium, magnesium, creatinine, blood urea nitrogen), complete blood count, coagulation panel, arterial blood gas, toxicology screen (blood, urine, gastric contents), thyroid function tests, cortisol level, and select cultures (blood, urine, throat, rectal, spinal fluid). Consider performing lumbar puncture after obtaining a computed tomography (CT) scan.
B. Diagnostic imaging. Cerebral CT findings reliably suggest intracranial hemorrhage, cerebral edema, mass lesions, focal infection, or hydrocephalus as diagnoses. Magnetic resonance imaging is preferred for the detection of abscess, tumor, subdural empyema, inflammatory lesions, or demyelinating diseases.
C. Other testing. Electroencephalography rules out seizures, status epilepticus (SE), and nonconvulsive SE. Lumbar puncture, typically after diagnostic imaging, may help determine increased intracranial pressure as well as infectious causes. Evoked potentials, such as brainstem auditory or short-latency somatosensory, provide information about the physiologic state and response to therapy (4).
The prognosis in comatose patients is typically poor except for those that are drug-related or result from traumas. In general, the longer the coma lasts, the poorer the prognosis. Coma rarely lasts longer than 4 weeks, after which, transition into a vegetative state or recovery occurs (3).
References
1. Plum F, Posner JB. The diagnosis of stupor and coma, 3rd ed. Philadelphia: FA Davis, 1983.
2. Feske SK. Coma and confusional states: emergency diagnosis and management. Neurol Clin North Am 1998;16:237–256.
3. Giacino JT. Disorders of consciousness: differential diagnosis and neuropathic features. Semin Neurol 1997;17:105–111.
4. Chiappa KH, Hill RA. Evaluation and prognostication in coma. Electroenceph Clin Neurophysiol 1998;106:149–155.
Read excerpts from these other book chapters related to Unconsciousness:
Copyright Details: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, Copyright © 2008 Williams & Wilkins.
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More About This Book:
Title: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter Authors: Robert B. Taylor (editor) Publisher: Lippincott Williams & Wilkins Copyright: 2000 ISBN: 0-78172-094-X 
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