Heat Stroke Encephalopathy Without the Presence of Distinct Imaging Findings: Case Report and Review of Literature

Heat stroke is a life‐threatening emergency characterized by severe hyperthermia and acute central nervous system (CNS) dysfunction. We describe a 72‐year‐old man who was found unresponsive in his vehicle on a day with ambient temperatures exceeding 90°F. On arrival, his core temperature was 105.8°F, and Glasgow Coma Scale (GCS) score was 5. Despite prompt initiation of active cooling and supportive care with normalization of body temperature, the patient developed persistent and fluctuating encephalopathy. Extensive metabolic, infectious, and toxicologic evaluations were unrevealing. Thyroid‐stimulating hormone was normal, arterial blood gases showed no acid–base derangements, ammonia and liver function tests were within normal limits, and urine toxicology was negative. Electroencephalography demonstrated diffuse cerebral slowing without epileptiform activity. Brain MRI performed approximately 1 week after admission under anesthesia, including diffusion‐weighted imaging, showed no acute abnormalities, revealing only mild age‐related atrophy and chronic small‐vessel ischemic changes. The patient′s neurologic function failed to recover over a prolonged hospitalization, and he ultimately died following transition to comfort‐focused care on hospital Day 27. This case highlights that severe and persistent encephalopathy may occur in the setting of probable heat stroke despite unrevealing conventional neuroimaging and underscores the diagnostic uncertainty and limitations of MRI in evaluating heat‐related neurologic injury.