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IM19.1-8 | Movement Disorders — Graded Quiz
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A 64-year-old man presents with a 3-year history of right-hand tremor. On examination: right-hand rest tremor 4–5 Hz that disappears when he reaches out, cogwheel rigidity of the right arm, bradykinesia on right finger-tapping, and a slightly stooped posture with reduced right arm swing. No Kayser-Fleischer rings. MRI brain is normal. He has no history of neuroleptic drug use. Applying the International Parkinson and Movement Disorder Society 2015 criteria, which of the following combinations is REQUIRED to make the clinical diagnosis of Parkinson's disease?
Correct. The IPMDS 2015 clinical diagnostic criteria for Parkinson's disease require bradykinesia as the mandatory (obligatory) feature, PLUS at least one of: rest tremor or rigidity. All four TRAP features do not need to be present simultaneously for the diagnosis. A levodopa challenge is supportive (and a positive response is a supportive criterion for 'clinically established PD'), but it is not required as a diagnostic gate. Normal MRI brain, absence of KF rings, no neuroleptic exposure — these exclusion criteria are also part of the clinical diagnostic process.
IPMDS 2015 PD diagnostic criteria: bradykinesia is mandatory + at least one of rest tremor or rigidity. Postural instability (the 4th TRAP feature) is not required for diagnosis — it is a late feature. Always apply absolute exclusion criteria (cerebellar signs, vertical gaze palsy, early severe autonomic failure, neuroleptic exposure) to exclude Parkinson-plus syndromes.
The IPMDS 2015 criteria mandate bradykinesia as the OBLIGATORY feature for PD diagnosis. At least one of rest tremor or rigidity must accompany it. Postural instability is not a required diagnostic feature (it is a late feature and the last T in TRAP). A positive levodopa response is a supportive criterion for 'clinically established PD' but not a gating requirement.
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A 55-year-old woman is evaluated for tremor. She has a 4-year history of tremor that was initially diagnosed as essential tremor and treated with propranolol with partial benefit. Over the past year she has developed slowness in daily activities, mild neck stiffness, and a quiet voice. On examination: hypomimia, bilateral cogwheel rigidity (left > right), mild bradykinesia, and a bilateral postural and rest tremor. Her propranolol was recently increased without improvement. Which feature in this case should MOST prompt a re-evaluation of the essential tremor diagnosis?
Correct. Essential tremor is characterised by a postural-kinetic tremor WITHOUT other parkinsonian features (no rigidity, no bradykinesia, no hypomimia). The emergence of cogwheel rigidity, bradykinesia, and hypomimia — signs of parkinsonism — fundamentally changes the diagnosis from ET to PD (which can have an action tremor component in addition to the rest tremor). This case illustrates the concept of 'PD masquerading as ET': early PD can present with predominant postural/action tremor, and the diagnosis becomes clear only as other TRAP features emerge. Propranolol partial response does not distinguish ET from PD.
Differential diagnosis of ET vs PD: ET = postural-kinetic tremor, NO rigidity, NO bradykinesia, NO hypomimia, positive family history, responds to propranolol or alcohol. PD = rest tremor + bradykinesia + rigidity (TRAP). Early PD can mimic ET; the emergence of any parkinsonian feature (rigidity, bradykinesia, hypomimia) should prompt re-evaluation.
Bilateral tremor is common in both ET and PD; partial propranolol response is non-specific. The diagnostic re-evaluation trigger here is the emergence of signs that are ABSENT in pure ET: cogwheel rigidity, bradykinesia, and hypomimia (masked facies). These are positive parkinsonian features that, combined with a tremor, meet IPMDS 2015 criteria for PD.
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A 72-year-old man with Parkinson's disease is prescribed levodopa-carbidopa. Three months later he is started on a medication for an unrelated chest infection. Within 48 hours he develops severe hyperthermia (39.8 C), confusion, hypertension, and diaphoresis. His levodopa was continued throughout. The new medication was linezolid (an antibiotic used for resistant gram-positive infections). Which pharmacological interaction BEST explains this life-threatening syndrome?
Correct. Linezolid is a weak, reversible MAO inhibitor (it inhibits both MAO-A and MAO-B as part of its mechanism). When combined with levodopa (or any serotonergic/dopaminergic drug), it can cause a hypertensive crisis and serotonin-dopamine syndrome due to catecholamine accumulation. This is an ABSOLUTE contraindication: levodopa must never be given with non-selective MAOIs (phenelzine, tranylcypromine) and caution is required with linezolid. The clinical presentation — hyperthermia, confusion, autonomic instability, diaphoresis — is consistent with this toxic interaction. Linezolid's MAO-inhibitory property is frequently overlooked in clinical practice.
Two most dangerous drug interactions in PD pharmacotherapy: 1. Levodopa + non-selective MAOI (phenelzine, tranylcypromine, or the antibiotic linezolid) = ABSOLUTE CONTRAINDICATION — hypertensive crisis and serotonin syndrome from catecholamine accumulation. 2. Dopamine agonists + antipsychotics (D2 blockers) = worsening parkinsonism.
Linezolid is a weak MAO inhibitor. Combined with levodopa, it causes catecholamine accumulation (dopamine, norepinephrine) that produces hypertensive crisis and features of serotonin-dopamine syndrome. COMT inhibitors (entacapone, tolcapone) block peripheral COMT, not MAO. The two most critical drug interactions in PD: levodopa + non-selective MAOI = absolute contraindication; levodopa + antipsychotic = exacerbates parkinsonism.
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A 28-year-old man presents with involuntary brief jerks of his limbs occurring predominantly in the morning, causing him to drop objects or spill drinks. He also has a history of generalised tonic-clonic seizures. EEG shows 3–4 Hz generalised spike-and-wave discharges. The limb jerks occur in clusters on waking. What movement disorder does this represent, and what is its aetiological classification?
Correct. Myoclonus consists of sudden, brief (< 100 ms), involuntary muscle jerks caused by abnormal neuronal discharges. Cortical myoclonus is the most common form and arises from cortical hyperexcitability. The clinical features here — brief limb jerks on waking, morning predominance, associated generalised tonic-clonic seizures, and generalised spike-and-wave on EEG — are pathognomonic of Juvenile Myoclonic Epilepsy (JME), a common idiopathic generalised epilepsy syndrome. The myoclonus in JME is cortical in origin. Chorea is non-rhythmic, flowing; tics are stereotyped and suppressible; dystonia is sustained posturing.
Myoclonus = sudden, brief (< 100 ms) involuntary muscle jerk from cortical, subcortical, spinal, or peripheral origins. Cortical myoclonus: JME (morning, waking, EEG spike-wave); Lance-Adams syndrome (post-anoxic, action-triggered); progressive myoclonic epilepsies. Differentiate from chorea (flowing, longer duration), tics (stereotyped, suppressible), and dystonia (sustained posturing).
Brief, sudden, involuntary jerks lasting < 100 ms = myoclonus (not chorea, tics, or dystonia). Cortical myoclonus on waking + generalised tonic-clonic seizures + spike-and-wave EEG in a young adult = juvenile myoclonic epilepsy. Tics are stereotyped and partially suppressible; chorea is flowing and non-rhythmic; dystonia is sustained posturing.
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A 38-year-old man presents with a 2-year history of progressive psychiatric symptoms (personality change, irritability, cognitive decline) followed by involuntary writhing movements of his face and limbs that are worsening. His father died at age 45 of a similar illness. Genetic testing confirms a CAG repeat expansion in the HTT gene. Neuroimaging shows caudate nucleus atrophy. Which of the following BEST characterises the movement disorder phenomenology in this condition?
Correct. This is Huntington's disease (HD) — autosomal dominant, CAG repeat expansion in HTT gene (>36 repeats pathological), caudate atrophy on MRI. The movement disorder is chorea: non-rhythmic, non-repetitive, flowing, dance-like involuntary movements that flow from one body part to another unpredictably. The pathophysiology is striatal degeneration predominantly affecting medium spiny neurons of the indirect pathway, which normally inhibit movement; their loss disinhibits the thalamo-cortical circuit, producing the hyperkinetic phenotype. Note: HD is a hyperkinetic-hypokinetic disorder; in advanced disease, rigidity and hypokinesia emerge (Westphal variant in juvenile-onset).
Huntington's disease: autosomal dominant, CAG>36 in HTT gene, caudate atrophy. Chorea = indirect pathway failure from striatal degeneration → thalamic disinhibition → hyperkinetic disorder. Psychiatric and cognitive features (irritability, depression, dementia) typically precede motor features by years. Tetrabenazine (VMAT2 inhibitor) is treatment for chorea.
Huntington's disease (HD) causes chorea — the classic hyperkinetic movement disorder. The pathophysiology is selective striatal neuron degeneration (indirect pathway neurons), causing indirect pathway underactivity and thalamic disinhibition. Chorea is non-rhythmic, non-repetitive, flowing movements — distinct from dystonia (sustained posturing) or myoclonus (brief jerks). HD is autosomal dominant (CAG repeat, HTT gene) with psychiatric/cognitive features preceding chorea.
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A 66-year-old man with a 7-year history of Parkinson's disease is assessed for surgical intervention. He has severe motor fluctuations (wearing off + dyskinesias) that are inadequately controlled on maximal medical therapy including levodopa, ropinirole, rasagiline, and entacapone. His cognitive function is intact (MoCA 27/30). MRI brain shows no significant cortical atrophy. He is considered for deep brain stimulation (DBS). Which of the following is the PRIMARY mechanism by which bilateral subthalamic nucleus (STN) DBS improves PD motor features?
Correct. In Parkinson's disease, loss of dopamine from the SNc leads to overactivation of the subthalamic nucleus (STN) via the indirect pathway. The overactive STN drives excessive excitatory output to GPi/SNr, which excessively inhibits the thalamus — resulting in bradykinesia and rigidity. High-frequency DBS of the STN (typically 130–185 Hz) functionally inhibits STN output (by mechanisms including depolarisation block of local neurons and axonal inhibition), thereby reducing GPi/SNr overactivity and restoring thalamic motor facilitation. DBS does not destroy neurons (unlike ablative procedures like pallidotomy) and is reversible. It significantly reduces motor fluctuations, dyskinesias, and 'off' time.
Deep brain stimulation (DBS) for PD: STN or GPi targets. STN-DBS: high-frequency stimulation functionally inhibits overactive STN, reducing GPi over-inhibition of thalamus. Indications: motor fluctuations + dyskinesias uncontrolled on maximal medical therapy, intact cognition, no significant comorbidity. Does NOT restore dopaminergic neurons or cure PD.
DBS does not destroy neurons — it functionally inhibits the overactive STN via high-frequency stimulation, which normalises downstream GPi/SNr activity. This reverses the circuit imbalance of PD: overactive STN → overactive GPi → excessive thalamic inhibition. By inhibiting STN, GPi activity normalises, thalamic inhibition decreases, and motor cortex activity is restored. STN-DBS is reversible and adjustable, unlike ablative procedures.
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A 52-year-old woman presents with a 2-year history of sustained twisting of her neck to the right (torticollis) causing significant pain and functional limitation. The movements worsen with stress and improve when she touches her chin with her finger (geste antagoniste). She has no family history of movement disorders and has not taken any dopamine-blocking drugs. What is the MOST likely diagnosis, and which investigation should FIRST be performed to exclude a structural cause?
Correct. Cervical dystonia (spasmodic torticollis) is the most common adult focal dystonia. It is characterised by sustained, involuntary contractions of the neck muscles causing abnormal posturing of the head (typically lateral rotation, tilt, or flexion/extension). The pathognomonic feature here is the geste antagoniste (sensory trick) — touching the chin or face provides sensory input that temporarily reduces the dystonia in over 70% of patients. Idiopathic cervical dystonia in adults without drug history warrants MRI brain and cervical spine to exclude a structural lesion (tumour, demyelination, vascular lesion) before labelling as primary dystonia. Botulinum toxin injection is the treatment of choice.
Cervical dystonia (spasmodic torticollis): sustained neck muscle contractions causing head deviation. Geste antagoniste (sensory trick) is pathognomonic. Idiopathic adult-onset focal dystonia: MRI to exclude secondary cause first. Treatment: botulinum toxin injection (first-line). Secondary dystonias: drug-induced (D2 blockers), Wilson's (young, KF rings), structural (brain lesion).
Sustained head turning with pain + geste antagoniste (touch relieves the abnormal posture) = cervical dystonia. This is the most common adult focal dystonia. It is NOT a tremor (which would be rhythmic oscillation), NOT a tic (which would be stereotyped and suppressible), and NOT drug-induced parkinsonism (which would have TRAP features). MRI brain + cervical spine is the first investigation to exclude structural (secondary) dystonia.
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A 30-year-old man presents with a 6-year history of multiple motor tics (eye blinking, shoulder shrugging, facial grimacing) and vocal tics (sniffing, throat clearing, and occasional coprolalia). Symptoms began in childhood and have waxed and waned. There is associated obsessive-compulsive behaviour. Which of the following BEST describes the tic disorder and the first-line pharmacological treatment for disabling tics?
Correct. Tourette syndrome (TS) is defined by multiple motor tics AND at least one vocal tic, present for more than 1 year (with onset before age 18), causing significant distress or functional impairment. Coprolalia (involuntary obscene vocalisations) is the most famous but least common (10–15%) feature of TS. Associated comorbidities include OCD and ADHD. Tics are characterised by being stereotyped, repetitive, partially suppressible (with a premonitory urge), and waxing-waning in severity. First-line pharmacological treatment for disabling tics: clonidine (alpha-2 agonist, fewer side effects) or low-dose fluphenazine/haloperidol (D2 blockers). Habit reversal training (behavioural therapy) is also first-line for mild tics.
Tourette syndrome: multiple motor + vocal tics, onset <18 years, duration >1 year, associated OCD/ADHD. Tics = stereotyped, repetitive, partially suppressible with premonitory urge. First-line for disabling tics: clonidine (alpha-2 agonist) or low-dose fluphenazine/haloperidol. Behavioural therapy (habit reversal training) for mild tics. Comorbid OCD responds to SSRIs.
Tourette syndrome = multiple motor + at least one vocal tic, onset in childhood, duration >1 year. Tics are stereotyped, partially suppressible (with a premonitory urge), and waxing-waning. Coprolalia is the hallmark but occurs in <15%. Valproate is for epilepsy; SSRIs treat the OCD comorbidity but not tics; ASO + benzathine penicillin is for Sydenham's chorea (post-streptococcal). First-line for disabling tics: clonidine or low-dose D2 blocker.
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A 19-year-old medical student rotates through the neurology ward. She sees a patient with Parkinson's disease (PD), another with multiple system atrophy (MSA), and a third with progressive supranuclear palsy (PSP). Which clinical feature, if present, would MOST reliably place the patient in the Parkinson-plus (atypical parkinsonism) category rather than idiopathic PD?
Correct. Vertical supranuclear gaze palsy (inability to move eyes downward or upward voluntarily, with preserved reflex eye movements to head turning) combined with early falls and axial (truncal) rigidity is the defining clinical feature of Progressive Supranuclear Palsy (PSP) — a Parkinson-plus syndrome. These features are absolute exclusion criteria for the diagnosis of idiopathic PD in the IPMDS 2015 criteria. Other red flags for Parkinson-plus include: early severe autonomic failure (MSA), cerebellar signs (MSA-C), alien limb phenomenon (corticobasal syndrome), and absence of any response to levodopa. Unilateral onset, pill-rolling tremor, and sustained levodopa response all support idiopathic PD.
Parkinson-plus syndromes (atypical parkinsonism) — red flags excluding idiopathic PD: PSP = vertical gaze palsy + early falls + axial rigidity; MSA = severe autonomic failure + cerebellar signs; corticobasal syndrome = alien limb + cortical sensory loss. All have poor levodopa response. DAT-SPECT cannot differentiate PD from Parkinson-plus (all show nigrostriatal degeneration).
Unilateral onset, pill-rolling rest tremor, and sustained levodopa response are supportive features of idiopathic PD. Vertical supranuclear gaze palsy + early falls + axial rigidity = PSP (a Parkinson-plus syndrome). Other absolute exclusion criteria for idiopathic PD: cerebellar signs (MSA-C), early severe dysautonomia (MSA), alien limb (corticobasal), neuroleptic drug use. Parkinson-plus syndromes respond poorly to levodopa.
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A 68-year-old woman with no prior medication history develops rigidity, bradykinesia, and a mask-like face 6 weeks after being started on metoclopramide 10 mg three times daily for nausea following gallbladder surgery. She has no tremor. DAT-SPECT is reported as normal. Which of the following conclusions is MOST appropriate?
Correct. Drug-induced parkinsonism (DIP) is caused by D2 receptor-blocking drugs: metoclopramide, domperidone, haloperidol, and other antipsychotics. Clinically, DIP mimics idiopathic PD with rigidity, bradykinesia, and mask-like face. The key distinguishing features are: (1) temporal relationship to a D2 blocker, (2) often bilateral and symmetric (unlike the asymmetric onset of idiopathic PD), (3) NORMAL DAT-SPECT (because the presynaptic nigrostriatal pathway is structurally intact — the postsynaptic D2 receptor is blocked pharmacologically but the dopamine transporter on presynaptic terminals is unaffected). Management: stop the offending drug; motor features usually improve over weeks to months. If DAT-SPECT were abnormal, it would indicate underlying nigrostriatal degeneration (idiopathic PD unmasked by the drug).
Drug-induced parkinsonism: bilateral, symmetric, no tremor, caused by D2 blockers (metoclopramide, haloperidol, domperidone). DAT-SPECT is NORMAL (presynaptic pathway intact). Stop the offending drug; recovery expected over weeks-months. If DAT-SPECT is abnormal despite drug withdrawal, suspect underlying idiopathic PD unmasked by the drug.
Normal DAT-SPECT in a patient with parkinsonism on a D2 blocker = drug-induced parkinsonism. The presynaptic nigrostriatal pathway (which DAT-SPECT images) is structurally intact; the parkinsonism is caused by postsynaptic D2 receptor blockade. Stop metoclopramide — symptoms typically resolve over weeks to months. If DAT-SPECT were abnormal, it would suggest underlying idiopathic PD unmasked by the drug.
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A 61-year-old man with Parkinson's disease undergoes a levodopa challenge test. Three hours after his morning dose he suddenly develops severe hyperthermia (40.2 C), altered consciousness, diffuse lead-pipe rigidity, and autonomic instability (BP 168/104, HR 118). His levodopa was inadvertently withheld for 36 hours before the test. Which of the following BEST describes this emergency and its immediate management?
Correct. Parkinsonism-hyperpyrexia syndrome (PHS) is a potentially fatal emergency precipitated by abrupt withdrawal or significant reduction of dopaminergic therapy in PD patients (analogous to neuroleptic malignant syndrome, NMS, which is triggered by D2 receptor blockade). Features: hyperthermia, severe rigidity (lead-pipe), impaired consciousness, and autonomic dysfunction (hypertension, tachycardia, diaphoresis). It is not caused by antipsychotics (NMS) — the trigger here is dopamine deficiency. Immediate management: (1) restore dopaminergic therapy urgently via nasogastric tube if the patient cannot swallow (NG levodopa), (2) supportive care — IV fluids, cooling, monitoring, ICU-level care. Dantrolene may be used for severe hyperthermia, but restoration of dopaminergic tone is the specific treatment.
Parkinsonism-hyperpyrexia syndrome (PHS): hyperthermia + severe rigidity + impaired consciousness after abrupt levodopa withdrawal. The dopamine-deficiency emergency — mirror image of NMS. Treatment: RESTORE dopaminergic therapy urgently (NG levodopa if unable to swallow) + supportive ICU care. NEVER abruptly stop levodopa in PD patients — taper if stopping is necessary.
Abrupt levodopa withdrawal causing hyperthermia + lead-pipe rigidity + autonomic instability in a PD patient = parkinsonism-hyperpyrexia syndrome (PHS). This is the dopamine-deficiency equivalent of NMS (which is caused by D2 blockade, not withdrawal). Treatment is urgent restoration of dopaminergic therapy (nasogastric levodopa), not levodopa cessation. Dantrolene and bromocriptine have been used adjunctively for hyperthermia and rigidity respectively.
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