The brain could be regarded as being in three parts. The brain stem is the most primitive part and sits above the spinal cord at the base of the rest of the brain. The brain stem plays a vital role in basic attention, arousal, and consciousness. All information to and from our body passes through the brain stem on the way to or from the brain. The brain stem is responsible for many of the functions that give us life such as breathing, heart function, sleep wake cycle, temperature control. Wrapped around this basic brain is the “limbic brain” or intermediate brain. It includes the hippocampus, thalamus, hypothalamus and amygdala which are involved in memory and much of the behaviour related to sex, hormones, food, fight or flight responses, the perception of pleasure and competition with others. The limbic brain is the seat of higher emotions including the protection of the young and feelings such as love, sadness and jealousy.
encephalitis presents with memory loss, personality changes, anxiety or depression, neuropsychiatric disturbances, partial or generalized seizures including status epilepticus, olfactory and gustatory hallucinations, sleep disturbances, and abnormalities in other homeostatic functions.
Infectious encephalitis – caused by direct invasion of the brain by an infectious agent, usually a virus. Auto-immune encephalitis – caused by the persons own immune system reacting against itself.
Physical examination findings assist in the localization of clinical symptoms and anatomical classification of specific paraneoplastic syndromes. Paraneoplastic limbic encephalitis: Anterograde or retrograde amnesia and neuropsychiatric disturbances predominate, with altered levels of consciousness at later stages. Focal neurologic deficits also may be noted. Focal encephalitis: Focal neurologic deficits occur and include aphasia and motor or sensory abnormalities. Epilepsia partialis continua or seizures may be evident. Brainstem encephalitis: Patients experience oscillopsia, diplopia, vertical and horizontal gaze abnormalities, facial numbness, dysarthria, hearing loss, and dysphagia. Motor neuron dysfunction: Patients have neck flexor/extensor weakness, asymmetric limb weakness, fasciculations, atrophy, and a combination of upper and lower motor neuron signs.