Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (83 page)

   Other disorders (e.g., leukodystrophies, lipid storage diseases, Bassen-Kornzweig syndrome)

   Nutritional deficiencies (e.g., vitamin B
₁₂
, thiamine, niacin, pyridoxine)

Endocrine Disorders

   Pancreas (diabetic coma, hypoglycemia)

   Thyroid (myxedema, thyrotoxicosis)

   Adrenal (Addison disease, Cushing syndrome, pheochromocytoma)

   Panhypopituitarism

   Parathyroid (hypofunction or hyperfunction)

Psychogenic Conditions That May Mimic Coma

   Depression, catatonia

   Malingering

   Hysteria, conversion disorder

Initial workup must be based on the clinical presentation. Rapid evaluation of treatable lesions, especially surgical, may improve survival. Conditions that may be mistaken for coma or stupor include the locked-in syndrome, akinetic mutism, and psychogenic unresponsiveness. In children, also consider complete paralysis with lesions of the brain stem, botulism, and Guillain-Barré syndrome.

   Laboratory Findings

Diagnosis is made on clinical examination, history, and urgent CT scan to rule out possible structural abnormalities such as papilledema, focal neurologic changes, acute stroke, expanding mass lesion, or herniation syndrome.

In patients with fever, a lumbar puncture should be performed to rule out bacterial meningitis or viral encephalitis. Neuroimaging prior to lumbar puncture in a comatose patient is recommended to avoid precipitating transtentorial herniation.
³
CSF may exclude subarachnoid hemorrhage (absence of xanthochromia) when CT is normal and may help in the diagnosis of demyelinating, inflammatory, and neoplastic disease with evaluation of glucose, cytology, and OCB.

Blood tests to exclude treatable causes of coma and stupor include the following:

   CBC

   Serum electrolytes, calcium, magnesium, phosphate, glucose, BUN, and creatinine