Neuroscience Clerkship at UH/VA
 

DIFFERENTIAL DIAGNOSIS OF COMA

METABOLIC VS STRUCTURAL ETIOLOGIES

Coma has an extensive differential diagnosis. However, the patient’s neurological examination can help determine if the coma is most likely due to a structural Vs a diffuse process.  The key to this is whether there are any focal findings on the neurological examination of the comatose patient. Focal findings on exam usually indicates a structural problem, whereas a non-focal exam usually indicates a diffuse process.  Some examples of structural processes include stroke, tumor or abscess. The best examples of diffuse processes are metabolic and toxic etiologies.  Below is a list of some of the more common etiologies of coma by category and whether they are non-focal versus focal findings on neurological exam.

Differential Diagnosis of Coma

Vascular

Infarction [usually focal findings]

Large MCA stroke with swelling and compression of the contralateral hemisphere

Bilateral cerebral infarction (e.g., multiple emboli)

Brainstem infarction (e.g., basilar stroke)

Cerebellar infarct with brainstem compression/hydrocephalus

Sinus venous thrombosis

Hemorrhage [usually focal findings]

Spontaneous

- Subarachnoid hemorrhage

[caution: SAH may be focal or non-focal]

- Intracerebral hemorrhage

Pons

Cerebellar with brainstem compression

Thalamic

Basal ganglia or lobar (with extension into the ventricles or compression of the contralateral hemisphere)

Trauma [usually focal findings]

Subarachnoid hemorrhage

[caution: SAH may be focal or non-focal]

Epidural hematoma (with herniation or mass effect on the contralateral hemisphere)

Subdural hematoma (bilateral; or with herniation or mass effect on the contralateral hemisphere)

Multiple contusions

Diffuse axonal shear injury

[caution: axonal shear injury may be focal or non-focal]
 

Neoplasm (with herniation) [usually focal findings]
 

Toxic [usually non-focal findings]

Cyanide

Ethylene glycol

Carbon monoxide

Others

 

Drugs [usually non-focal findings]

     Alcohol

Barbiturates

[caution: Barbiturates may cause extraocular movement deficits]

Benzodiapezines

Opiates

Anticholinergics

Phencyclidine

Others


Metabolic [usually non-focal findings]

Hypoxia

Hypercapnia

Hypo/hypernatremia

Lactic acidosis

Hypercalcemia

Hypermagnesemia

Wernicke's encephalopathy

[caution: Wernicke's may cause ocular abnormalities and gait disturbance]

Hepatic encephalopathy

Uremia
 

Endocrine [usually non-focal findings]

Hypoglycemia
    
[caution: hypoglycemia may cause focal findings in some patients]

Hyperglycemic non-ketotic coma

Diabetic ketoacidosis

Myxedema (hypothyroidism)

Addisonian crisis
 

Infections

[caution: all may be focal or non-focal]

Bacterial meningitis

Fungal meningitis

Tuberculous meningitis

Syphilitic meningitis

Viral encephalitis
 

Anoxia (shock) [usually non-focal findings]

Fat embolism

[caution: may be focal or non-focal]
 

Hypertensive encephalopathy [usually focal findings]
 

Hydrocephalus

[caution: may be focal or non-focal]
 

Status epilepticus

[caution: may be focal or non-focal]

Post-ictal state

[caution: may be focal or non-focal]