Question 86#

A 45-year-old woman presents complaining of visual disturbance. Examination reveals a left congruous homonymous hemianopia.

Where is the lesion most likely to be? 

A. Optic chiasm

Correct Answer D: 

Visual field defects The main points for the exam are:

• Left homonymous hemianopia means visual field defect to the left, i.e. Lesion of right optic tract
• Homonymous quadrantanopias: PITS (Parietal-Inferior, Temporal-Superior)
• Incongruous defects = optic tract lesion; congruous defects = optic radiation lesion or occipital cortex

A congruous defect simply means complete or symmetrical visual field loss and conversely an incongruous defect is incomplete or asymmetric.

Homonymous hemianopia: 

• Incongruous defects: lesion of optic tract
• Congruous defects: lesion of optic radiation or occipital cortex
• Macula sparing: lesion of occipital cortex

Homonymous quadrantanopias*: 

• Superior: lesion of temporal lobe
• Inferior: lesion of parietal lobe
• Mnemonic = PITS (Parietal-Inferior, Temporal-Superior)

Bitemporal hemianopia: 

• Lesion of optic chiasm
• Upper quadrant defect > lower quadrant defect = inferior chiasmal compression, commonly a pituitary tumour
• Lower quadrant defect > upper quadrant defect = superior chiasmal compression, commonly a craniopharyngioma

*This is very much the 'exam answer'. Actual studies suggest that the majority of quadrantanopias are caused by occipital lobe lesions. Please see the following link for more details: http://www.ncbi.nlm.nih.gov/pubmed/9109741

Question 87#

A 5-year-old boy is diagnosed as having absence seizures.

What is the chance he will be seizure free by the age of 16-years-old?

A. 5-10%

Correct Answer E: Absence seizures - good prognosis: 90-95% become seizure free in adolescence.

Absence seizures:

Absence seizures (petit mal) are a form of generalized epilepsy that is mostly seen in children. The typical age of onset of 3-10 years old and girls are affected twice as commonly as boys.

Features: 

• Absences last a few seconds and are associated with a quick recovery
• Seizures may be provoked by hyperventilation or stress
• The child is usually unaware of the seizure
• They may occur many times a day
• EEG: bilateral, symmetrical 3Hz spike and wave pattern

Management: 

• Sodium valproate and ethosuximide are first-line treatment
• Good prognosis - 90-95% become seizure free in adolescence

Question 88#

A 67-year-old man is reviewed in the neurology clinic due to concerns about increasing clumsiness. Examination reveals an ataxic gait and increased upper limb tone with cog-wheel rigidity. Blood pressure is 135/80 lying and 95/70 standing.

What is the most likely diagnosis?

A. Motor neuron disease

Correct Answer E: Whilst postural hypotension may be seen in Parkinson's disease the ataxic gait point towards a diagnosis of multiple system atrophy.

Multiple system atrophy:

Shy-Drager syndrome is a type of multiple system atrophy.

Features: 

• Parkinsonism
• Autonomic disturbance (atonic bladder, postural hypotension)
• Cerebellar signs

Question 89#

A 66-year-old woman is investigated for ascites and found to have ovarian cancer. She presents due to 'unsteadiness'. On examination there is evidence of nystagmus and past-pointing.

Which one of the following antibodies is most likely to be present?

A. Anti-Hu

Correct Answer B: This lady has developed cerebellar syndrome secondary to anti-Yo antibodies.

Paraneoplastic syndromes affecting nervous system:

Lambert-Eaton myasthenic syndrome: 

• Associated with small cell lung cancer (also breast and ovarian)
• Antibody directed against pre-synaptic voltage gated calcium channel in the peripheral nervous system
• Can also occur independently as autoimmune disorder 

Anti-Hu: 

• Associated with small cell lung carcinoma and neuroblastomas
• Sensory neuropathy - may be painful
• Cerebellar syndrome
• Encephalomyelitis

Anti-Yo: 

• Associated with ovarian and breast cancer
• Cerebellar syndrome

Anti-GAD antibody: 

• Associated with breast, colorectal and small cell lung carcinoma
• Stiff person's syndrome or diffuse hypertonia

Anti-Ri:

• Associated with breast and small cell lung carcinoma
• Ocular opsoclonus-myoclonus

Question 90#

Which one of the following is least recognized as a cause of autonomic neuropathy?

A. Guillain-Barre syndrome

Correct Answer B: 

Autonomic neuropathy:

Features: 

• Impotence, inability to sweat, postural hypotension
• Postural hypotension e.g. drop of 30/15 mmHg
• Loss of decrease in heart rate following deep breathing
• Pupils: dilates following adrenaline instillation

Causes: 

• Diabetes
• Guillain-Barre syndrome
• Multisystem atrophy (MSA), Shy-Drager syndrome
• Parkinson's
• Infections: HIV, Chagas' disease, neurosyphilis
• Drugs: antihypertensives, tricyclics
• Craniopharyngioma