IM19.1-8 | Movement Disorders — Practice Quiz

Correct. A tremor that is present at rest and disappears with voluntary movement is a rest tremor — the hallmark of basal ganglia disease, specifically dopaminergic neuron loss in the substantia nigra pars compacta (SNc). SNc neurons project to the striatum via the nigrostriatal pathway; their loss reduces dopaminergic facilitation of the direct pathway and disinhibition of the indirect pathway, resulting in increased GPi/SNr inhibitory output to the thalamus and the classical motor features of Parkinson's disease: rest tremor, rigidity, bradykinesia, and postural instability.

The single most important clinical distinction in movement disorders is the activation condition of tremor. Rest tremor (disappears with voluntary movement) = basal ganglia disease, Parkinson's disease until proved otherwise. Intention tremor (worsens at target-reach) = cerebellar disease.

The key distinguishing feature is that this tremor disappears during voluntary movement (i.e., it is a rest tremor). Rest tremor is the signature of dopaminergic deficiency at the level of the substantia nigra pars compacta — not cerebellar or corticospinal pathology. Intention tremor (worsens at end of voluntary movement) indicates cerebellar dysfunction; action tremor includes postural and kinetic subtypes.

Correct. The direct pathway (striatum → GPi/SNr, inhibitory) normally suppresses GPi/SNr activity, which disinhibits the thalamus and facilitates movement. Dopamine from the SNc acts on D1 receptors on striatal medium spiny neurons of the direct pathway and facilitates this inhibitory output to GPi. Net result: reduced GPi inhibition of the thalamus → thalamus more active → motor cortex facilitated → movement promoted. This is why dopamine deficiency in PD leads to excessive GPi inhibition of the thalamus — bradykinesia.

The basal ganglia circuit operates through opposing direct (pro-movement, D1-mediated) and indirect (anti-movement, D2-mediated) pathways. Net output from GPi/SNr inhibits the thalamus; dopamine from SNc biases toward direct pathway facilitation, promoting movement.

Dopamine from the SNc biases the basal ganglia circuit toward pro-movement by facilitating the direct pathway (D1) and inhibiting the indirect pathway (D2). Facilitation of the direct pathway reduces GPi inhibitory output to the thalamus, thereby promoting movement. In PD, dopamine deficiency reverses this — the indirect pathway predominates, GPi/SNr over-inhibit the thalamus, and voluntary movement is suppressed.

Correct. This is essential tremor (ET) — the most common movement disorder. ET is characterized by a bilateral postural and kinetic tremor (present during voluntary maintained posture and movement) that is absent at rest. The absence of rigidity, bradykinesia, and postural instability excludes Parkinson's disease. A positive family history (autosomal dominant pattern in ~50% of cases) is characteristic. ET is treated with propranolol (first-line) or primidone.

Tremor classification by activation state: rest tremor (at rest, suppressed by movement) = PD; postural tremor (on maintained posture) and kinetic tremor (during movement) = essential tremor or physiological tremor; intention tremor (worsens at target-reach) = cerebellar disease.

The tremor is a postural/action tremor (present on outstretched arms, absent at rest), not a rest tremor. Rest tremor is the hallmark of PD. The absence of rigidity and bradykinesia further excludes parkinsonism. The positive family history supports essential tremor, the most common movement disorder, classified as a postural-kinetic action tremor.

Correct. Peak-dose dyskinesias (PDDs) are choreiform (dance-like) involuntary movements that occur at the time of maximum plasma levodopa concentration — typically 1 to 2 hours after an oral dose. They reflect excessive striatal dopaminergic stimulation at peak plasma levels and are a major long-term complication of levodopa therapy, occurring in over 50% of patients after 5 years of treatment. Management options include reducing individual levodopa dose (with increased frequency), switching to controlled-release formulations, adding amantadine, or considering deep brain stimulation.

Levodopa long-term complications: peak-dose dyskinesias (choreiform movements at maximum plasma level), end-of-dose wearing off (parkinsonian features as levels fall), and on-off fluctuations (unpredictable switches). All occur after 5+ years of levodopa, driven by progressive disease and pulsatile dopaminergic stimulation.

The timing — 1 hour after the dose (i.e., at peak levodopa plasma concentration) — and the choreiform character identify this as peak-dose dyskinesia. End-of-dose wearing off occurs as levodopa levels fall and presents as a return of parkinsonian features (rigidity, bradykinesia), not choreiform movements. On-off fluctuations are unpredictable motor switches not reliably time-locked to dose.

Correct. This is Wilson's disease (hepatolenticular degeneration) — an autosomal recessive disorder of copper transport (ATP7B mutation) causing copper accumulation in the liver, brain, cornea (Kayser-Fleischer rings), and kidneys. The diagnostic triad here is: neuropsychiatric features (tremor, dysarthria, dystonia) + Kayser-Fleischer rings on slit-lamp + low serum ceruloplasmin (<20 mg/dL). First-line treatment is D-penicillamine (copper chelator); trientine is an alternative for those intolerant of penicillamine. Zinc salts are used for maintenance. Wilson's is a critical diagnosis in any patient under 40 with movement disorders because it is treatable and reversible if caught early.

Wilson's disease = KF rings (slit-lamp) + low ceruloplasmin (<20 mg/dL) + elevated 24-hour urinary copper. Always consider Wilson's in any patient under 40 with movement disorder — it is treatable. D-penicillamine is first-line; trientine for penicillamine intolerance.

Kayser-Fleischer rings on slit-lamp examination, low serum ceruloplasmin (<20 mg/dL), and onset in a teenager with movement disorder and neuropsychiatric features = Wilson's disease. This is a treatable cause of movement disorder; D-penicillamine (copper chelation) is the first-line therapy. Levodopa is for dopaminergic deficiency states; haloperidol is not appropriate here; propranolol is for essential tremor.

Correct. Sydenham's chorea is one of the five major criteria of acute rheumatic fever (Jones criteria). It results from molecular mimicry: antibodies against Group A streptococcal antigens cross-react with basal ganglia (particularly striatal) neuronal antigens, causing immune-mediated neuronal dysfunction. The chorea is characteristically non-rhythmic, non-repetitive, random-appearing ('dancing'), involving face, limbs, and trunk — the classic hyperkinetic movement disorder in this age group. The elevated ASO titre and post-streptococcal timing confirm the diagnosis. Treatment involves secondary prophylaxis with benzathine penicillin; choreiform movements usually resolve over weeks to months.

Chorea in children: Sydenham's chorea (post-streptococcal, ASO elevated, Jones criteria major manifestation) vs Huntington's disease (adult onset, autosomal dominant CAG repeat). Chorea = non-rhythmic, non-repetitive, flowing dance-like movements — hallmark hyperkinetic disorder of basal ganglia dysfunction.

The clinical features — non-rhythmic, non-repetitive, random dance-like movements in a child 2–4 weeks after a streptococcal throat infection — are diagnostic of Sydenham's chorea. This is an immune-mediated (molecular mimicry) disorder affecting the basal ganglia as part of acute rheumatic fever. Tics (Tourette's) are stereotyped and suppressible; myoclonus is sudden brief muscle jerks; PD is a hypokinetic disorder of adults.

Correct. Metoclopramide is a D2 receptor blocker (dopamine antagonist) used as a prokinetic and antiemetic. Chronic D2 blockade at the striatum disrupts basal ganglia circuit modulation, causing sustained involuntary muscle contractions that produce the twisted, abnormal postures characteristic of dystonia. Drug-induced dystonia can be acute (within days) or tardive (after months of treatment). Other D2 blockers causing drug-induced movement disorders include haloperidol, domperidone, and prochlorperazine. Cessation of the offending drug and, if needed, anticholinergics (benztropine) or tetrabenazine are the management options.

Drug-induced movement disorders to know: D2 blockers (metoclopramide, haloperidol, prochlorperazine) cause acute dystonia (sustained twisting postures), drug-induced parkinsonism (TRAP features), akathisia (inner restlessness), and tardive dyskinesia (stereotyped orofacial/limb movements after months). Always take a drug history in any new movement disorder.

Metoclopramide is a D2 receptor blocker. Sustained abnormal posturing (twisting the neck and trunk) = dystonia, not tardive dyskinesia (which presents as stereotyped, repetitive orofacial/limb movements after chronic exposure). Drug-induced movement disorders from D2 blockers include: acute dystonia, drug-induced parkinsonism, akathisia, and tardive dyskinesia. The drug history is critical — always ask about antiemetics, antipsychotics, and prokinetics in any patient with a new movement disorder.

Correct. End-of-dose wearing off (the 'wearing off' phenomenon) occurs when the clinical benefit of each levodopa dose diminishes before the next dose is due — the patient notices their parkinsonian features (tremor, stiffness, slowness) return predictably as plasma levodopa levels fall. The first-line management strategies include: (1) increase dose frequency (smaller doses more often), (2) add a COMT inhibitor (entacapone or opicapone) to block peripheral levodopa metabolism and extend plasma half-life, or (3) add a MAO-B inhibitor (rasagiline, selegiline) to reduce central dopamine breakdown. Delayed gastric emptying (accelerated by high-protein meals) can worsen wearing off by delaying levodopa absorption.

Levodopa motor complications: wearing off = predictable, dose-related return of PD features as plasma levels fall; treat by increasing dose frequency or adding COMT inhibitor. On-off = unpredictable, random motor switches; dyskinesias = choreiform movements at peak dose. These reflect progressive disease with altered dopamine receptor sensitivity.

End-of-dose wearing off is the predictable re-emergence of parkinsonian features as plasma levodopa levels fall before the next scheduled dose. It is distinguished from on-off fluctuations (unpredictable switches unrelated to dose timing) by its dose-related predictability. The first management step is shortening the dosing interval or adding a COMT inhibitor (entacapone) to extend levodopa's effect.

Correct. The parkinsonian gait is highly characteristic and an important bedside diagnostic observation: stooped (flexed) posture, reduced arm swing (often asymmetric at onset — ipsilateral to the tremor side), small shuffling steps, en bloc turning (turning the whole body in multiple small steps rather than pivoting on a foot), festination (involuntarily accelerating small steps as if chasing the centre of gravity), and freezing episodes. This gait pattern reflects the combination of bradykinesia, rigidity, and postural instability that defines PD. Watching the patient walk in through the door before formal examination often allows the examiner to characterise the movement disorder.

The most powerful single observation in a movement disorder consultation is watching the patient walk before formal examination. Parkinsonian gait: stooped posture, asymmetric reduced arm swing, shuffling steps, festination, en bloc turning — reflects bradykinesia + rigidity + postural instability of the TRAP syndrome.

Wide-based staggering gait = cerebellar ataxia; high-stepping with foot drop = lower motor neuron/peripheral nerve disease; scissor gait with spasticity = upper motor neuron/pyramidal disease. The parkinsonian gait (stooped posture, reduced asymmetric arm swing, shuffling small steps, festination, en bloc turning) is distinct and reflects basal ganglia dysfunction.

Correct. DAT-SPECT (also known as DaTscan) images the dopamine transporter in the nigrostriatal pathway. In Parkinson's disease (and other parkinsonian syndromes involving nigrostriatal degeneration), DAT-SPECT shows reduced uptake in the striatum — classically an asymmetric 'comma' or 'period' shape of the putamen instead of the normal 'comma' bilaterally. In essential tremor, which does not involve nigrostriatal degeneration, DAT-SPECT is normal. This is the most specific functional imaging investigation for differentiating ET from PD when clinical assessment is inconclusive. MRI brain is normal in typical idiopathic PD and cannot differentiate; serum ceruloplasmin is used for Wilson's disease.

Imaging in movement disorders — selection principles: typical idiopathic PD = no imaging needed (clinical diagnosis); atypical parkinsonism or PD vs ET uncertain = DAT-SPECT (abnormal in nigrostriatal degeneration, normal in ET); young patient with movement disorder = MRI brain + serum ceruloplasmin + 24-h urinary copper (exclude Wilson's).

Brain MRI is normal in idiopathic PD and does not differentiate it from ET. DAT-SPECT is the investigation of choice for this specific question: it images the presynaptic dopamine transporter in the nigrostriatal pathway and is abnormal (reduced uptake) in PD/parkinsonism but normal in ET. Serum ceruloplasmin is used for Wilson's disease (young patient with movement disorder + low ceruloplasmin + KF rings).