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]
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