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An Exercise in Diagnosis
Two cases are presented. We have used a systematic approach as shown in Fig. 2 to illustrate its usefulness in clinical practice.
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Figure 2.
Emergent diagnosis and care of the comatose patient.
Case 1
A middle-aged man was brought into the emergency department after being found prone and unresponsive for an unknown period. Because of vomiting, tachypnea (respiratory rate of 28), with no protection of his airway, the patient was intubated in the field. No further history was available. The patient was afebrile. Blood pressure was 148/89 with a heart rate of 85.
On physical examination, the patient appeared thin. Skin exam showed rare spider telangiectasias over the chest. The patient smelled faintly sweet. Neurologic examination revealed a comatose patient (GCS 3T, FOUR Score E0M0B4R3). The examination was otherwise nonlocalizing. The emergent CT scan was normal.
With a normal CT scan, the potential etiologies include toxic, epileptic, infectious, endocrine/metabolic, and anoxic/ischemic. The emergent EEG was normal, ruling out status epilepticus. Routine laboratory investigation revealed a normal complete blood count including normal leukocyte count, which rules out infection assuming a normal immune system. Thyroid stimulating hormone and glucose were normal, ruling out the most common causes of endocrine/metabolic coma.
With all other possibilities ruled out, intoxication remains the most likely explanation for the patient's unresponsiveness. Electrolytes were normal except for slightly low calcium, mildly elevated AST and ALT with normal ammonia and bilirubin, and slightly elevated creatinine. Osmol and anion gaps were significantly elevated at 29 and 19, respectively. The significant elevations in the anion and osmol gap indicate the presence of an unmeasured anion, particularly an atypical alcohol. In this case, ethylene glycol taken by a chronic alcoholic is the correct diagnosis.
Case 2
A middle-aged man was brought into the emergency department after being found prone and unresponsive for an unknown period. Breathing was described as erratic with periods of apnea and the patient was intubated in the field. No further history was available. The patient was afebrile. Blood pressure and heart rate were stable and required no treatment.
On physical examination, the patient was comatose (GCS 4T, FOUR Score E0M1B2R1). General examination was normal. Cranial nerve examination revealed a right pinpoint pupil that was reactive to light and a left midposition pupil that was unreactive to light. Corneal reflex was absent on the left. Cough and gag reflexes remained intact. Motor examination showed bilateral extensor posturing to painful stimuli. An emergent CT scan was normal.
Laboratory workup, including complete blood count, full electrolyte panel, liver function tests, arterial blood gases, and thyroid function test, was normal. Osmol and anion gaps were normal. Urine drug screen was negative.
Given the physical examination findings, the lesion localized to the brainstem, but was more diffuse (pontine pupil on the right and midbrain pupil on the left). With a normal CT scan and normal laboratory investigation, the lesion was likely the result of an embolus to the basilar artery. This was confirmed with a CT angiogram and resulted in urgent endovascular retrieval.
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