temporal lobe

The temporal lobe lies beneath the lateral sulcus and is bordered by the frontal and parietal lobes superiorly and the occipital lobe posteriorly. Key structures include the primary auditory cortex (Heschl's gyrus, Brodmann areas 41/42), Wernicke's area (typically in the posterior superior temporal gyrus of the dominant hemisphere, Brodmann area 22) responsible for language comprehension, and the medial temporal lobe structures—hippocampus, amygdala, and entorhinal cortex—crucial for declarative memory consolidation and emotional regulation.

Clinical significance: Lesions to Wernicke's area cause receptive (fluent) aphasia, characterized by impaired comprehension with fluent but nonsensical speech (word salad) and poor repetition. Bilateral hippocampal damage (e.g., in HSV encephalitis, which has a predilection for temporal lobes, or after bilateral medial temporal lobectomy as in patient H.M.) causes anterograde amnesia. The amygdala is implicated in fear conditioning and emotional memory; bilateral amygdala damage (Urbach-Wiethe disease) causes loss of fear recognition.

Temporal lobe epilepsy is the most common form of focal epilepsy in adults, often arising from mesial temporal sclerosis (hippocampal sclerosis). Seizures may present with auras (déjà vu, olfactory hallucinations, rising epigastric sensation), automatisms (lip-smacking, picking motions), and post-ictal confusion. It is frequently associated with febrile seizures in childhood history.

Other associations: Klüver-Bucy syndrome (bilateral temporal lobe/amygdala damage) presents with hyperorality, hypersexuality, disinhibition, and docility—classically tested with HSV encephalitis. Herpes simplex encephalitis characteristically affects the temporal and inferior frontal lobes, presenting with fever, altered mental status, and seizures, often with hemorrhagic necrosis seen on MRI.