The frequency of alpha waves seen in EEG recordings is:
B. Alpha, beta, delta, and theta are four important wavelets in EEG when awake. Alpha waves are predominant, especially posteriorly when the eyes are closed; they occur at a frequency of 8 to 13 Hz. Beta waves are sometimes seen in normal EEG over central, anterior regions; they occur at a frequency higher than 13 Hz. Theta activity is seen infrequently when awake but often when a subject is drowsy or sleeping. Excessive theta when awake is abnormal. Delta waves (frequency less than 3.5 Hz) are normally seen only in deep sleep and are pathological if noted in adult waking EEG. With aging, slow waves become more common in EEG.
Reference:
Diffuse flattening of EEG with low-amplitude theta and delta waves is seen in:
A. Huntington’s disease is characterized by diffuse flattening or loss of alpha waves in EEG. In a study conducted in a group of 95 patients with Huntington’s chorea, 31 showed little activity of any kind (fl at trace EEG) and in particular no alpha rhythm above 10 µV in amplitude was seen. There was a statistically significant association between cortical atrophy, especially the frontal lobe, and a ‘low voltage’ EEG in the same study. Such low-voltage records, though not specific for Huntington’s chorea, are rare in other neurological disorders.
Which of the following functions is mediated by endogenous cannabinoids?
E. Two types of cannabinoid receptors, central (CB1) and peripheral (CB2), have been identified. Both receptors bind to exogenously administered tetrahydrocannabinol (THC), present in marijuana. Anandamide (from the Sanskrit word ‘ananda’ for bliss) is chemically N-arachidonoylethanolamine (arachidonic acid and ethanolamine derivative). It is a weak endogenous cannabinoid ligand. 2-arachnidonylglycerol is a strong endogenous ligand for the cannabinoid receptor. Endogenous cannabinoids exhibit intraocular pressure-lowering effects. They also decrease motor activity level and relieve pain. Anandamides are demonstrated in the thalamus, with a putative role in pain-related neurotransmission.
A 22-year-old man is diagnosed with craniopharyngioma. He is experiencing symptoms due to the tumour pressing upon adjacent brain tissue.
Which of the following visual defect is characteristic of this tumour?
D. Bitemporal hemianopia is secondary to chiasmatic lesions. Pituitary tumours characteristically cause bitemporal hemianopia. Craniopharyngioma is a benign epithelioid tumour arising from remnants of Rathke’s pouch at the junction of the infundibular stem and pituitary. It lies above the sella turcica and so exerts pressure effects on the optic chiasm leading to bitemporal hemianopia. Tunnel vision is a result of extensive peripheral fi eld defects. Quadrantanopias usually result from damage to the optic radiation beyond the chiasma. Parietal lesions result in inferior, while temporal lesions result in superior, quadrantanopia.
Priapism is a side-effect associated with which of the following?
C. Priapism is defined as a persistent penile erection greater than 4 hours in duration, which is unrelated to sexual stimulation or desire. Roughly 40 to 50% of patients who develop priapism become impotent, even after surgical treatment. Drug-induced priapism accounts for 15–40% of all cases. Psychotropics associated with priapism include trazodone, phenothiazines, butyrophenones, risperidone, and clozapine. Priapism results from decreased venous outflow from the corpora cavernosa of the penis. This can be caused by obstruction of the venous system, for example by blood dyscrasias such as sickle cell anaemia or by blocking the sympathetically mediated (α1 receptor) detumescence. Hence the ability of a drug to block α1 receptors correlates with its risk of priapism. This is especially true if the antiadrenergic effect is unopposed by an equally strong anticholinergic effect. Sympathetic tone is related to detumescence while parasympathetic tone is related to erection. For drugs with combined antiadrenergic and anticholinergic activity, when antiadrenergic activity negates detumescence, the anticholinergic activity will negate erection and so priapism will be rare.
Click to expand