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Question 1

Catecholamine degradation

Answer 1

Enzymatic degradation occurs via catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO).

MAO can be blocked by MAO inhibitors to elevate catecholamine concentration in synaptic cleft.

3,4-Dihydroxyphenylacetic acid (DOPAC) is a neuronal metabolite formed by the breakdown of dopamine by monoamine oxidase.

Vanillylmandelic acid (VMA) is an end-stage metabolite. Urinary excretion is elevated in patients with pheochromocytoma and neuroblastoma.

Question 2

Phenylketonuria

Answer 2

A congenital disorder characterized by the accumulation of phenylalanine in the central nervous system.

Can be caused by a defect of phenylalanine hydroxylase (classic PKU) or deficiency in tetrahydrobiopterin (malignant PKU).

Causes psychomotor retardation, seizures, a musty odor, and pale skin/hair (from lack of melanin production).

Question 3

Cushing disease

Answer 3

Patient with signs of Cushing syndrome: weight gain with central obesity, abdominal striae, hypertension, hyperpigmentation, and irregular menses. A positive low-dose dexamethasone suppression test indicates hypercortisolism.

A serum ACTH within the reference range in this context is considered abnormal, as ACTH secretion should physiologically be suppressed by elevated serum cortisol levels.

Suppression of ACTH with high-dose dexamethasone confirms increased ACTH production from the pituitary gland (Cushing disease).

Question 4

Chromaffin cells

Answer 4

Neuroendocrine cells that originate from the neural crest and migrate to the paraganglia and adrenal medulla during embryonic development.

Question 5

Zona glomerulosa

Answer 5

The response of the zona glomerulosa to angiotensin II is attenuated by low serum potassium or high serum sodium levels

Question 6

Angiotensin-converting enzyme (ACE)

Answer 6

Bradykinin is degraded by angiotensin-converting enzyme (ACE), a component of the renin-angiotensin-aldosterone system (RAAS).

ACE is produced by cells of the pulmonary endothelium. Circulating bradykinin is therefore primarily metabolized in the pulmonary vasculature.

Question 7

Hypoglycemia in diabetics

Answer 7

(Relative) overdose of insulin or a noninsulin drug is by far the most common cause of hypoglycemia.

Consider factitious disorder in patients with access to insulin and other diabetes medications (e.g., healthcare professionals), for whom there is no other obvious explanation for hypoglycemia.

Recurrent hypoglycemia → changes in the counterregulatory autonomic response (e.g., decreased epinephrine release) → lower glucose threshold needed to trigger symptoms → asymptomatic hypoglycemia

Beta blockers can mask signs of hypoglycemia

Question 8

Hypoglycemia: Neurogenic/autonomic symptoms

Answer 8

ncreased sympathetic activity: tremor, pallor, anxiety, tachycardia, sweating, and palpitations
Increased parasympathetic activity: hunger, paresthesias, nausea, and vomiting

Question 9

Hypoglycemia: Neuroglycopenic symptoms

Answer 9

Agitation, confusion
Seizure
Somnolence → obtundation → stupor → coma → death
Beta blockers can mask signs of hypoglycemia

Question 10

Communicating hydrocephalus

Answer 10

Pathophysiology Clinical features Diagnosis

Communicating hydrocephalus

↑ CSF production
↓ CSF absorption

Typical findings of raised ICP
Headache, nausea, and vomiting
Papilledema
Abducens nerve palsy
Abnormal gait
Impaired consciousness
Cushing triad (irregular breathing, widening pulse pressure, bradycardia)

Ultrasonography (children ≤ 18 months of age)
MRI or CT (older children and adults)

Communicating hydrocephalus can also be a complication of subarachnoid hemorrhage.

Communicating hydrocephalus: All ventricles are dilated

Question 11

Noncommunicating hydrocephalus

Answer 11

Obstructed passage of CSF from the ventricles to the subarachnoidal space

Noncommunicating hydrocephalus: Ventricles upstream of the obstruction are dilated

Question 12

Normal pressure hydrocephalus (NPH)

Answer 12

↓ CSF absorption

Classic triad
Wet: urinary incontinence
Wacky: dementia
Wobbly: frequent falls, broad-based gait with short, shuffling steps (gait apraxia)

MRI (initial test)
CSF tap test

Normal pressure hydrocephalus does not manifest with signs of increased ICP (e.g., headache, papilledema)

NPH is diagnosed based on typical clinical features, evidence of communicating hydrocephalus on imaging, and normal or only mildly elevated opening pressure

Patients can develop a flat affect due to disruption of frontal lobe circuits, particularly the dorsolateral prefrontal cortex and its connections.

Question 13

Hydrocephalus ex vacuo

Answer 13

Loss of brain tissue

Symptoms of the underlying condition (e.g., Alzheimer disease, Pick disease)

Cortical atrophy may be prominent on imaging.

Question 14

Cushing reflex

Answer 14

A hypothalamic response to maintain cerebral perfusion in patients with elevated ICP.
Results in the Cushing triad, which consists of increased systolic blood pressure, bradycardia, and irregular breathing

Question 15

Tension headache

Answer 15

Photophobia/phonophobia (may occur)
No nausea, no vomiting
Autonomic symptoms are absent (lacrimation, rhinorrhea, sweating)

Question 16

Chronic hydrocephalus

Answer 16

Signs of upper motor neuron damage (e.g., spasticity, hyperreflexia) are common in advanced, chronic hydrocephalus due to stretching of the motor cortices and pyramidal tracts around the dilated ventricles.

The lower extremities are typically affected because the cortical regions responsible for processing the motor functions of the lower extremities are located in the medial precentral gyrus (according to the motor homunculus), which is the most stretched part of the primary motor cortex in patients with hydrocephalus.