Transient diffuse cerebral hypoperfusion in Tc-99m HMPAO SPECT of the brain during withdrawal syndrome following acute barbiturate poisoning.

A 29-y-old man had taken small daily doses of barbiturates as hypnotics (50 mg pentobarbital, 30 mg phenobarbital) for 4 y with no evident intoxication. When he attempted suicide by ingestion of 15 g amobarbital, treatment with charcoal hemoperfusion resulted in rapid disappearance of drug from the blood. Generalized convulsions and delirium ensued; these were responsive to phenobarbital. An electroencephalogram (EEG) showed diffuse S-Hz theta activity. Tc-99m hexamethylpropyleneamineoxime (HMPAO) single photon emission computed tomographic (SPECT) imaging of the brain demonstrated a diffuse bilateral decrease in blood flow to the cerebral cortex. These investigations were performed interictally on day 4 without sedative drugs, prior to initiation of anticonvulsants, and at a time when barbiturates were no longer detected in the serum. An EEG on day 15 no longer showed abnormal slowing. On the other hand, Tc-99m HMPAO SPECT of the brain demonstrated residual cerebral hypoperfusion on day 20, with nearly full recovery of cerebral perfusion on day 51. Barbiturate withdrawal syndrome is presumed to reQuire a history of abuse; however in patients with a history of treatment with barbiturates physicians treating acute barbiturate poisoning should be alert for the possibility of barbiturate withdrawal syndrome even in the absence of barbiturate abuse.