Diencephalon and Limbic System Flashcards
Korsakoff’s syndrome
degeneration of mammillary neurons
commonly associated with thiamine deficiency associated with chronic alcoholism.
Usually preceded by Wenicke’s encephalopathy which includes mental changes, abnormal eye movements, and gait ataxia. These patients have neuronal changes in the anterior vermis of the cerebellum, in gaze centers or ocular neurons in the midbrain and pons, and in the mediodorsal nuclei of the thalamus.
Patients have anterograde short-term memory loss, which may be combined with retrograde amnesia and confabulations in which patients make up stories about events that never occurred.
Lesions of the ventromedial hypothalamus
may result in obesity
lesions of the lateral hypothalamus pro due aphagia
lesion of the posterior hypothalamus
patients may have a body temperature that varies with the environmental temperature like a poikilotherm (cold-blooded)
lesion of the anterior hypothalamus
may have hyperthermia
Calcification in the CNS
the pineal gland is the most common site of calcification in the CNS and may be used as a diagnostic marker in imaging. Pineal calcification may reduce the output of melatonin and be a cause of insomnia
Pineal tumors
may cause obstruction of CSF flow, increased intracranial pressure, and a noncommunicating hydrocephalus.
Compression of the upper midbrain, pretectal area, or a posterior commissure by a pineal tumor may cause Parinaud’s syndrome in which patient may have impaired conjugate vertical gaze and pupillary light reflex abnormalities
Olfactory deficits
may be incomplete (hyposmia), distorted (dysosmia), or complete (anosmia) and result from transport problems by damage to the primary olfactory neurons or to neurons in the olfactory pathways in the CNS.
head injuries that fracture the cribiform plate may tear the central processes of olfactory nerve fibers as they pass through the plate to terminate in the olfactory bulb or may injure the bulb itself
seizures and the hippocampus
the lack of inhibitory neurons in hippocampal structures makes this region more susceptible to seizures than other cortical areas.
Neural degeneration in patients with Alzheimer’s
characterized by an accumulation of neurofibrillary tangles and senile plaques and occurs initially in the entorhinal cortex and then in the subiculum and CA1 region of the hippocampus proper.
The basal nuclei of Meynert, limbic nuclei of the thalamus, neurons in association cortical areas, and noradrenergic and serotoninergic neurons in the brainstem are affected later. Primary sensory and motor cortical areas are spared as are cranial nerve nuclei and the cerebellum
Dementia in Alzheimer’s
impaired memory for events in time is often the leading symptom, followed by intellectual decline, language deficits, which may lead to an aphasia, and changes in mood or personality
as the dementia progresses, deficits in orientation, reasoning, judgment, and the ability to abstract, calculate, and use language become evident.
routine activities may be handled reasonably well, but the patient fails to respond as well to new or altered situations. Patients may confabulate and deny or hide their deficits.
GABA neurons
in the basolateral nuclei are sensitive to GABA agonists, which enhance GABA transmission and reduce anxiety
Kluver Bucy Syndrome
results from bilateral lesions to or ablation of the amygdala and hippocampus. Patients with amygdala lesions in this syndrome become placid, exhibiting a marked decrease in aggressive behavior, and show little emotional reaction to external stimuli.
These patients may exhibit hypermetamorphosis in which visual objects are repeatedly approached as though they were completely new. These patients may have increased oral exploratory behavior in which they put everything in their mouths, eating only appropriate objects and become hypersexual.
If the hippocampus is involved, patients may have anterograde amnesia. Rostral temporal lobe lesions may also affect the lateral part of the visual radiation and result in a contralateral homonymous superior quadrantanopsia.
