What are the causes of stupor?

Causes of Stupor

Stupor results from either structural brain lesions, metabolic/toxic encephalopathies, or psychiatric conditions—with metabolic causes being most common in clinical practice. 1

Metabolic and Toxic Causes

The most frequent etiologies of stupor are metabolic disturbances, which should be your first consideration:

• Hepatic encephalopathy causes stupor at West Haven Grade 3, characterized by triphasic waves on EEG and often preceded by asterixis at earlier grades (which disappears as stupor develops). 1, 2
• Hyperglycemic crises (DKA and HHS) produce stupor through severe osmotic derangements, with HHS more commonly causing stupor/coma than DKA (stupor/coma occurs when effective serum osmolality exceeds 320 mOsm/kg). 1
• Uremic encephalopathy from renal dysfunction produces progressive slowing of background EEG rhythms and can present with triphasic waves similar to hepatic encephalopathy. 3
• Drug intoxications and toxins including benzodiazepines, opiates, lithium, valproate, baclofen, and anticholinergics can produce stupor with characteristic EEG patterns (burst suppression, alpha coma, spindle coma). 1, 4, 3
• Hypoxia produces stupor with various abnormal EEG patterns including burst suppression and alpha coma patterns. 3
• Electrolyte disturbances particularly hyponatremia, hypokalemia, and hypomagnesemia can cause stupor. 4

Structural Brain Lesions

Structural causes must be excluded urgently as they may require neurosurgical intervention:

• Supratentorial lesions including intracranial mass effect, globally elevated intracranial pressure, chronic subdural hemorrhage, and subarachnoid hemorrhage produce stupor with focal EEG abnormalities (delta/theta activity, attenuation of faster frequencies). 1, 3
• Infratentorial lesions (brainstem strokes, cerebellar masses) can cause stupor but may show normal EEG, particularly with pontine lesions—making clinical examination critical. 3
• Hydrocephalus causes stupor through increased intracranial pressure. 1

Infectious Causes

• Meningitis and encephalitis cause stupor through direct CNS inflammation, with disturbances of consciousness ranging from confusion to coma. 1
• Systemic infections (urinary tract infections, pneumonia) are the most common precipitating factors for metabolic encephalopathies leading to stupor, particularly in elderly patients. 1

Seizure-Related Causes

• Nonconvulsive status epilepticus is a critical diagnosis requiring EEG verification, as patients appear stuporous with minimal or no motor movements—this is easily missed without EEG monitoring. 1, 3
• Post-ictal states following generalized seizures can produce prolonged stupor. 1

Psychiatric Causes

• Catatonic stupor is characterized by psychomotor disturbances including stupor, catalepsy, waxy flexibility, mutism, negativism, and posturing—it is diagnostically non-specific and can occur in schizophrenia, bipolar disorder, or medical conditions. 1, 5
• Catatonic stupor responds to benzodiazepines or ECT, not neuroleptics, making correct diagnosis essential. 5

Rare but Important Causes

• Idiopathic recurrent stupor (endozepine stupor) presents with unpredictable episodes of stupor with fast EEG activity, responds dramatically to flumazenil, and is caused by increased endogenous benzodiazepine-like compounds (endozepine-4). 6, 7, 8
• Parasitic infections including neurocysticercosis and other helminthic infections can cause stupor through mass effect or inflammation. 1
• Acute disseminated encephalomyelitis (postinfectious/postimmunization) causes abrupt neurologic symptoms including stupor several days after viral illness or vaccination. 1

Critical Diagnostic Pitfalls

• Delirium is distinct from stupor—delirium involves inattention and fluctuating consciousness but does not occur in severely reduced arousal states like stupor or coma. 1
• Locked-in syndrome mimics stupor but patients are fully conscious with intact vertical eye movements—this requires careful neurological examination to distinguish. 3
• Triphasic waves on EEG are frequent in hepatic encephalopathy but are not specific and occur in uremia, hyponatremia, and drug intoxications. 1
• Always obtain EEG in unexplained stupor to exclude nonconvulsive status epilepticus, which requires immediate treatment. 3