A neuropsychologist administers a test to a 21-year-old man with a change in personality related to brain damage. The patient is asked to name the colour of a word while ignoring the actual word.
What test is being administered?
E. The question describes the classic form of the Stroop Colour–Word Test. In this test the subject is initially required to read names of some basic colours. Later the subject is asked to name the colours of geometrical shapes. Following this, the test of interference is applied. Looking at a colour name written in a different colour produces a conflict; this makes the subject read the name instead of saying the colour in which it is written, for example if the word ‘blue’ is written in green the subject tends to say blue, even when asked to name the displayed colour. The classic form of the Stroop Colour–Word Test is the most commonly used, though variations such as Emotional Stroop are now available. Rorschach’s is a projective test which uses ink-blot images. The Continuous Performance Test measures sustained/selective attention and impulsivity.
Reference:
Which of the following is the rate-limiting enzyme in the synthesis of dopamine?
A. Dopamine is synthesized from the amino acid tyrosine. Initially, tyrosine is converted to L-dihydroxyphenylalanine (L-DOPA) by tyrosine hydroxylase (the rate-limiting step). L-DOPA is rapidly converted to dopamine by dopa decarboxylase. Dopamine is stored in vesicles and 80% of the released dopamine is rapidly transported back into the nerve terminal by a dopamine-specific transporter (DAT). This intracellular extravesicular dopamine is metabolized by monoamine oxidase (MAO) to dihydroxyphenylacetic acid (DOPAC). Twenty percent of the released dopamine is sequentially degraded extracellularly by catechol-O-methyltransferase (COMT) and MAO to 3-methoxytyramine (3-MT) and homovanillic acid (HVA). Dopaminergic cell bodies in the brain are mainly localized in the ventral tegmental area in the brainstem. There are predominantly four pathways that are considered to be dopaminergic in the brain: mesocortical and mesolimbic axons originate from the VTA and project to the prefrontal cortex and limbic structures, respectively; the tuberoinfundibular pathway mediates release of prolactin from the pituitary; and the nigrostriate pathway forms an integral part of the basal ganglion extrapyramidal system.
A 55-year-old patient presents with bilateral hand tremors that worsen with stress.
Which of the following features of the tremor is suggestive of benign essential tremor rather than Parkinsonism?
C. Parkinsonian tremor is usually of large amplitude with a frequency of 4 to 6 cycles per second. It is a resting tremor which persists even during action. Parkinsonian tremor is not reduced by alcohol but is exaggerated in stressful situations. In contrast, benign essential tremor is usually of smaller amplitude and higher frequency (10 to 12 cycles per second). It is often seen during action and may be unnoticeable during rest. It is exacerbated by stress, similar to Parkinsonian tremor. Clinically, essential tremor is similar to exaggerated physiological tremor.
A 50-year-old woman, being treated for depression as an outpatient, presents to A&E with acute-onset, severe headache. She describes this as the ‘worst headache’ she has ever had in her life. She insists on switching off the lights in the examination cubicle. Her blood pressure is 150/90 mmHg. When asked to get up from the examination couch, she complains of neck stiffness. An emergency CT scan is normal.
The next most appropriate step is:
D. The patient described here has acute, severe headache, photophobia, and meningism. These features are highly suggestive of subarachnoid haemorrhage (SAH). A CT scan is not 100% sensitive in ruling out possible intracranial bleed. Given the high clinical suspicion, the gold standard test for SAH, lumbar puncture, must be carried out. Presence of depression must not distract one from considering acute medical causes of somatic complaints such as headaches. Haloperidol is not indicated in this scenario. Please note that if the CT scan discloses a subarachnoid haemorrhage, lumbar puncture need not be carried out as a routine.
A 68-year-old woman has long-standing hypertension. She is diagnosed to have somatization disorder by her GP and is prescribed venlafaxine 225 mg/day. Unfortunately she develops a cerebrovascular accident. While being treated for stroke at the acute neurology unit, she starts having severe, ‘gruesome’ pain on her left side of the body.
The pain has an intense, scalding quality. The most likely site of infarct is:
C. This patient is having an infarct of the thalamus. Thalamic infarcts affecting ventral posterolateral nucleus and posteromedial nucleus result in a severe sensory syndrome characterized by intense burning pain, hyperaesthesia, or hemianaesthesia affecting the contralateral body. Cold thermal stimuli, emotional stress, and loud sounds may aggravate the painful state. Despite this apparent hypersensitivity, the patient shows an elevated pain threshold requiring a stronger than usual stimulus to produce a sensation of pain (hypoalgesia with hyperpathia). This thalamic pain syndrome is also called Dejerine–Roussy syndrome. Some patients may develop hemiataxia and choreoathetosis.
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