In early Alzheimer’s disease, widespread loss of nerve cells is most pronounced in which of the following structures?
D. Early in the Alzheimer’s disease neuronal loss is most pronounced in layer II of the entorhinal cortex of the hippocampus. The parahippocampal gyri and subiculum are also affected. This extends to anterior nuclei of the thalamus, septal nuclei, amygdala, and monoaminergic systems of the brainstem are also depleted. The cholinergic neurones of the nucleus basalis of Meynert are also reduced. In cerebral cortex, most pronounced loss occurs with respect to pyramidal neurones and astrocytic proliferation follows as a compensatory or reparative process, most prominently in layers III and V.
Reference:
Glutamate-induced excitotoxicity is proposed as a cause of which of the following conditions?
A. Excessive stimulation of glutamate receptors leads to an increase in intraneuronal calcium and nitric oxide. Calcium activates proteases that could destroy the neurone from within. Memantine is an NMDA antagonist used in the treatment of Alzheimer’s disease, based on the excitotoxicity hypothesis. This mechanism may be applicable for Parkinson’s disease too. In Huntington’s disease, an expansion of the polyglutamine region of huntingtin takes place due to the disease-causing mutation. Hence the mutant huntingtin protein accumulates in the nuclei of neurones, preferentially in striatum and cortex. These aggregates may be directly toxic to some extent, but predominant striatal loss, as opposed to cortical loss, may be due to glutamate-mediated excitotoxicity. Huntingtin accumulation may render cells unusually sensitive to glutamate-mediated damage.
Which of the following is a feature of occlusion of the right-sided posterior inferior cerebellar artery?
D. Posterior inferior cerebellar artery occlusion leads to Wallenberg’s syndrome. The resulting signs and symptoms are attributed to infarction of a wedge of lateral medulla that contains vestibular nuclei, descending sympathetic tract, spinothalamic system (carrying pain and temperature from contralateral side of body), descending fi fth nerve tract and nucleus, and ninth and tenth nerve fibers of same side. This leads to ipsilateral Horner’s syndrome (miosis, anhidrosis, and ptosis due to sympathetic damage), ipsilateral loss of face sensation (fi fth nerve damage), dysphagia, hoarseness, loss of gag refl ex (ninth/tenth nerve damage), and contralateral loss of pain and temperature over half of the body.
A 65-year-old man presents with memory difficulties and loss of balance. He has significant, new-onset urinary incontinence. CT scan of the brain shows dilated ventricles but no significant widening of sulci.
The most likely diagnosis is:
A. The age of the patient, the triad of memory difficulties, loss of balance, and urinary incontinence, and the neuroimaging findings suggest normal-pressure hydrocephalus (NPH). NPH is not a hydrocephalus in the true sense—there is no increase in intracranial pressure when lumbar puncture is carried out. Following certain meningeal insults, secondary to subarachnoid haemorrhage, head trauma, or resolved meningitis, an increase in intracranial pressure may develop but reach a stable stage where formation of CSF diminishes and equilibrates with absorption, which increases proportionate to the pressure. Once this equilibrium is reached there must be a gradual fall in pressure, although at a high normal level. In some patients, this high normal intracranial pressure of 150 to 200 mm H2O leads to manifestation of NPH.
During polysomnographic recording of a patient with sleep disturbances, it is observed that his heart rate and blood pressure are lower than that recorded during normal wakefulness. His muscle tone is also notably low.
Which of the following is true with respect to his physiological state?
B. The presence of low heart rate, muscle tone, and blood pressure is suggestive of NREM sleep. At this stage of sleep if a person is awakened, he will be confused. He may not recollect the instance of awakening in the morning. A normal adult spends nearly 75% of sleep in various NREM stages, while the remaining 25% is REM sleep. Penile erection, high cerebral blood fl ow, and vividly recalled dreams are features of REM stage.
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