Electroencephalogram (EEG) is a commonly used diagnostic test. Which of the following statements regarding EEG is NOT correct?
E. An electroencephalograph represents cerebral cortical activity. EEG depends on afferent neural inputs from subcortical structures, including the thalamus and brainstem reticular formation. The thalamic afferents to the cortex are responsible for the alpha rhythm and sleep spindles usually seen in the second stage of NREM sleep. EEG is rarely specific to an illness because different conditions often produce non-specific and similar changes. Hypsarrythmia is associated with infantile spasms (West’s syndrome). Three-Hz spike-and-wave activity is associated with typical absence attacks. Generalized multiple spikes and waves (poly-spike wave) are associated with myoclonic epilepsy. Certain parts of the cerebral cortex, such as inferior temporal lobe, are inaccessible to routine electrode placement.
Reference:
A 32-year-old school teacher is admitted for constipation and acute abdominal pain. She experiences visual and tactile hallucinations with intense anxiety. She develops motor weakness of her legs on administration of hypnotics and diclofenac.
Which of the following laboratory tests is indicated?
D. This scenario depicts acute intermittent porphyria (AIP). It is one of the groups of disorders of haem metabolism, characterized by neurological and psychiatric manifestations without obvious cutaneous markers. AIP manifests itself by abdomen pain, neuropathies, and constipation, but, unlike most types of porphyria, patients with AIP do not have a rash. It is an autosomal dominant disorder with presentation starting between ages 18 and 40. It is episodic in nature and the episodes are often triggered by certain medications including oestrogens, barbiturates, and benzodiazepines. Diclofenac can precipitate an episode. Psychiatric manifestations include depression, anxiety, delirium, and psychosis. The most important lab. test is demonstrating increased urinary porphobilinogen during acute attacks. Treatment is aimed at reducing haem synthesis by administering haemin.
Which of the following is NOT helpful in differentiating pseudoseizures from true epileptic seizures?
E. All of these features except a history of seizure disorder may help to differentiate seizures from pseudoseizures. Pseudoseizures are more common in patients with epilepsy than those without. So having an established diagnosis of epilepsy does not rule out pseudoseizures. Patients with pseudoseizures do not have the characteristic prolactin elevation noted after an episode of true seizure; they may have unusually prolonged seizures with asymmetric limb involvement but without bladder or bowel control being lost.
Clozapine is strongly associated with fatal agranulocytosis. Which of the following is true regarding clozapine-induced agranulocytosis?
A. Incidence of agranulocytosis in patients on clozapine is less than 1 per 100 patients. The peak occurrence of agranulocytosis with clozapine is between 4 and 18 weeks after initiation of treatment. Weekly monitoring of the white cell or absolute neutrophil count is required for 18 to 26 weeks in most countries, with the frequency decreasing to biweekly or monthly thereafter. It is noted that the risk of clozapine-induced agranulocytosis is equivalent to the risk of agranulocytosis due to any other antipsychotic after 1 year of safe treatment. With regular monitoring, agranulocytosis can usually be detected before infection sets in. Discontinuation of clozapine, treatment with granulocyte colony stimulating factors, and vigorous treatment of infection are usually effective in restoring the white cell numbers. In UK, the Clozaril patient monitoring service (CPMS) maintains central laboratory data of all patients on Clozaril (generic form: clozapine) and sends one of three ‘traffic light signals’ to clinicians. Amber light is a sign of caution and a count should be repeated. With a red light, clozapine should be immediately stopped and re-challenge should not be done under normal circumstances.
Which one of the following statements regarding the dexamethasone suppression test is FALSE?
B. Exogenous administration of the steroid dexamethasone usually inhibits endogenous cortisol secretion. This cortisol suppression by the exogenous dexamethasone is impaired in patients with depression. This is thought to be due to a disturbed feedback mechanism among cortisol, adrenocorticotropic hormone (ACTH), and corticotrophin releasing hormone (CRH). Dexamethasone suppression is non-specific for depression and is also observed in patients with mania, schizophrenia, dementia, and other psychiatric disorders. There is some evidence to show that patients with dexamethasone non-suppression (test positive) respond well to physical interventions such as antidepressant therapy or electroconvulsive therapy compared to test negative population, though this is not widely replicated.
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