(MCQS 277-279) :A 15 year old girl complains of a one year history of vomiting and a nocturnal cough

Question:277
Correct Answer: D
Explanation:
tricyclic antidepressants TCAs produce a wide variety of toxic effects. The most severe toxicity occurs in the cardiovascular system and central and peripheral nervous systems. Cardiovascular toxicity results from direct myocardial depression, cardiac conduction disturbances, effects on peripheral vasomotor tone, and changes in the autonomic nervous system. TCAs bind to and inhibit the fast-sodium channel, thereby slowing phase O depolarization in His-Purkinje and ventricular myocytes. This results in slowed cardiac conduction (eg, prolonged QRS on the ECG), impaired cardiac contractility (via impaired cellular calcium entry), and possible ventricular dysrhythmias (caused by nonuniform sodium channel blockade). The sodium channel blockade present in TCAs is mitigated by larger concentrations of extracellular sodium (overcome competitive blockade) and alkalemia. TCAs block phase 3 repolarization in His-Purkinje myocytes, which results in prolonged QTc on the ECG. TCAs inhibit alpha 1-adrenergic receptors, resulting in peripheral vasodilation and orthostatic hypotension. TCAs block norepinephrine reuptake in the CNS and peripheral nervous system (PNS)(autonomic ganglia). Initially, this may result in hypertension and tachycardia. However, with prolonged blockade of reuptake, norepinephrine is depleted from the presynaptic nerve terminal (most norepinephrine released is from a recycled neurotransmitter), which results in refractory hypotension and bradycardia. Neurologic toxicity results from CNS blockade of muscarinic acetylcholine, H1-histamine, and GABA receptors; inhibition of norepinephrine, serotonin, and dopamine reuptake; and blockade of neuronal fast-sodium channels. Specifically, seizures likely are mediated by inhibition of norepinephrine reuptake, neuronal fast-sodium channel blockade, and GABA and N-methyl-D-aspartate (NMDA)-glutamate receptor blockade. TCAs are potent, competitive antagonists at central and peripheral muscarinic acetylcholine receptors. They readily produce anticholinergic stigmata, particularly central anticholinergic delirium.

Question:278
Correct Answer: I
Explanation:
The most common epileptic syndromes that are refractory to medical management are those associated with complex partial seizures. Complex partial seizures arise most commonly from the temporal lobe with the most frequent histologic substrate (found in approximately 65% of temporal lobectomy specimens) being mesial temporal sclerosis (MTS). Mesial temporal lobe epilepsy (or hippocampal epilepsy) may be the most common of these syndromes. Patients with mesial temporal lobe epilepsy tend to present months after onset of seizures, because the events are often associated with symptoms not generally believed to be epileptic. Patients often report a vague feeling of dysphoria, impending doom, or de ja vu with a strange epigastric sensation, while others report a stereotypic intrusion of a memory or thought. These initial manifestations are then followed by an alteration of consciousness. Observers note that the patient has a look of fear or confusion, and then stereotypic automatisms such as non-purposeful movement of the hands, feet, and/or mouth. The total duration of the seizure is usually about 90 seconds to 2 minutes. Seizures often cluster with 2-3 seizures per day for a day or two, followed by several seizure-free days. Although the seizures may be very unusual appearing, the stereotypic nature of the progression of clinical seizures may be striking. Patients with mesial temporal lobe epilepsy often have normal EEGs between seizures, especially early in the course of the disorder. MRI scans may demonstrated evidence of decreased volume of the mesial temporal lobe structures (hippocampus) on the effected side, with increased T2 signal, especially on the thin coronal images. Occasionally tumors affecting the mesial temporal structures are seen in these patients. Therefore, neuroimaging is indicated even when the patient’s seizures are not intractable. Because some patients with mesial temporal epilepsy do not remember their seizures, patients who experience a decline in memory function should be considered to possibly have experienced an exacerbation in seizure frequency until proven otherwise. This is a type of epilepsy that does not respond well to medication but is curable with surgery is more common than physicians suspected. This type of epilepsy, called mesial temporal lobe epilepsy, is caused by an abnormality in the brain's hippocampus. Eighty to 90 percent of patients with this disorder will become seizure free after surgery. The seizures and their effects on the patient become more severe over time with this epilepsy. Virtually all patients with seizures that are not controlled by two or three of the most common epilepsy drugs should undergo high resolution MRI evaluations looking for this abnormality. Hippocampal sclerosis or mesial temporal sclerosis is seen in most of the cases. The concept of mesial temporal lobe epilepsy syndrome is valid for selecting the patients with medically refractory but surgically remediable epilepsy for earlier surgical intervention. Temporal lobe epilepsy is a form of what is called focal epilepsy i.e. the fit is confined to one area of the brain, in this case the part of the brain called the temporal lobe. With this form of epilepsy, consciousness is not usually lost, although it may be impaired, but the hallmark of temporal lobe epilepsy is that the person experiences hallucinations or odd feelings of some description. For instance they may experience a smell, taste or sound that does not exist, or they may get a very strong feeling of re-living an experience. They may also carry out certain actions over which they have no control and do not remember afterwards.

Question:279
Correct Answer: B
Explanation:
Achalasia is a disorder characterized by functional obstruction at the oesophagogastric junction secondary to increased resting lower esophageal sphincter pressure, failure or incomplete relaxation of the lower esophageal sphincter with swallowing, and absence of or abnormal peristalsis in the body of the esophagus on swallowing. Achalasia is rare in children. The incidence is one case per 10,000 and fewer than 5% manifest symptoms before the age of 15 years. There is an equal male and female incidence. The mean duration of symptoms prior to diagnosis is approximately 28 months. For a long time lesions of Auerbach's plexus had been believed to be responsible for the motility disorder. Intramural nerve fibers are also involved. There is a deficiency of argyrophil ganglion cells which are believed to be essential for the coordination of peristalsis and for the stimulation of argyrophobe cells to release acetylcholine. Muscular changes are more discreet and are compatible with denervation atrophy. There is also degeneration and disappearance of peripheral vagal nerve cells in the presence of lesions in the dorsal vagal nucleus in the brain stem. There are some reports of familial inheritance with an autosomal recessive inheritance pattern. The primary site of involvement is probably the extrinsic neural structures and not in the esophagus itself. Presenting symptoms include regurgitation, dysphagia, retrosternal pain, weight loss or failure to thrive, choking sensations, recurrent pneumonias, and nocturnal cough. These patients are often described as slow eaters, consuming large amounts of fluid while eating. Diagnosis is by chest x- ray, barium swallow, and esophageal motility studies. Barium swallow shows a grossly dilated esophagus with tapering at the gastroesophageal junction sometimes referred to as a 'bird's beak'. There is also absence of contraction waves, poor emptying of the esophagus, and tertiary esophageal contractions. Routine chest x- ray may show a mediastinal widening and air fluid levels within the mediastinum. Esophageal motility studies will show and elevated lower esophageal sphincter pressure with failure to relax with swallowing. Approximately 90% of patients will have less than a 20% decrease in lower esophageal sphincter pressure with swallowing. Manometric studies will confirm absent or low amplitude contraction waves in the body of the esophagus.


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