Neuroscience-III Module — Final Year MBBS

AIM LEARNING CYCLE • FINAL YEAR MBBS • NEUROSCIENCE-III

Student Memory Support

Topic 5: Movement Disorders, Parkinson’s Disease & Ataxia

High-Yield Flashcards • Mnemonics • Memory Tables • Rapid Revision • Clinical Hooks • KMU Exam Points

1. High-Yield Flashcards

Tap each question to reveal the answer.

What are the three major clinical categories of movement disorders?

Hypokinetic, hyperkinetic and ataxic movement disorders.

What is the essential motor abnormality required for the diagnosis of parkinsonism?

Bradykinesia, together with resting tremor or rigidity.

Which neuronal degeneration causes the principal dopamine deficiency in Parkinson’s disease?

Degeneration of dopaminergic neurons in the substantia nigra pars compacta.

What pathological protein accumulates in Lewy bodies?

Aggregated alpha-synuclein.

Why is carbidopa combined with levodopa?

It inhibits peripheral dopa decarboxylase, increasing levodopa availability to the brain and reducing peripheral adverse effects.

What are wearing-off fluctuations in Parkinson’s disease?

Return of motor symptoms before the next scheduled levodopa dose as the duration of benefit shortens.

Which important behavioral adverse effect is associated with dopamine agonists?

Impulse-control disorders, such as compulsive spending or gambling.

What distinguishes intention tremor from Parkinsonian resting tremor?

Intention tremor increases as the limb approaches a target; resting tremor is most apparent when the limb is supported and relaxed.

What is dysmetria?

Inaccurate judgment of movement distance, causing overshooting or undershooting of a target.

Which examination finding favors sensory ataxia rather than cerebellar ataxia?

Marked worsening of balance when the eyes are closed, particularly with impaired proprioception.

Why does sudden severe cerebellar ataxia require urgent assessment?

It may indicate posterior circulation stroke or hemorrhage, potentially complicated by brainstem compression.

What movement pattern characterizes chorea?

Brief, irregular, non-rhythmic involuntary movements that flow unpredictably between body parts.

Which genetic abnormality causes Huntington’s disease?

An autosomal dominant CAG repeat expansion in the HTT gene.

What is the principal acute treatment for dopamine-blocker-induced dystonia?

Withhold the causative medication and administer an appropriate parenteral anticholinergic, such as benztropine or diphenhydramine. Assess the airway urgently if compromised.

2. Mnemonics

Mnemonic 1 — Core Motor Features of Parkinson’s Disease

TRAP

T — Tremor at rest
R — Rigidity
A — Akinesia / Bradykinesia
P — Postural instability

Remember: bradykinesia plus rest tremor or rigidity is required for parkinsonism; postural instability may appear later.

Mnemonic 2 — Important Cerebellar Signs

DANISH

D — Dysdiadochokinesia
A — Ataxia
N — Nystagmus
I — Intention tremor
S — Scanning speech
H — Heel-to-shin impairment

These findings reflect impaired cerebellar coordination rather than simple muscle weakness.

Mnemonic 3 — Recognizing Acute Dystonia

TOO

T — Torticollis
O — Oculogyric crisis
O — Opisthotonus

Following dopamine-blocking medication, sustained abnormal postures suggest acute dystonia. Stridor or breathing difficulty requires emergency airway assessment.

3. Memory Tables

Cerebellar vs Sensory vs Vestibular Ataxia

Feature	Cerebellar	Sensory	Vestibular
Primary defect	Coordination	Proprioception	Balance apparatus
Gait	Broad-based, irregular	Visual guidance dependent	Unsteady, may veer
Eye closure	Unsteady even with eyes open	Marked worsening	May worsen
Limb coordination	Dysmetria, intention tremor	Improves with visual guidance	Usually preserved
Associated clue	Dysarthria, nystagmus	Reduced joint-position sense	Vertigo, nausea

4. Rapid Revision Points — Last-Minute Revision

Must Remember:

Hypokinetic disorders reduce movement; hyperkinetic disorders produce excessive involuntary movements.
Bradykinesia is essential for the diagnosis of parkinsonism.
Parkinson’s disease involves degeneration of dopaminergic substantia nigra neurons.
Levodopa/carbidopa is the most effective symptomatic treatment for Parkinson’s motor dysfunction.
Long-term levodopa treatment may cause wearing-off, on–off fluctuations and dyskinesias.
Dopamine agonists may cause daytime sleepiness, hallucinations and impulse-control disorders.
Dysmetria, intention tremor and impaired alternating movements indicate cerebellar dysfunction.
Sudden severe ataxia requires urgent assessment for cerebellar stroke or hemorrhage.
Chorea produces irregular, flowing movements; Huntington’s disease may also cause cognitive and psychiatric symptoms.
Acute drug-induced dystonia follows dopamine receptor blockade and may respond rapidly to parenteral anticholinergic treatment.

5. Clinical Memory Hooks

Clinical Hook 1 — Parkinsonism

Asymmetric slowness + rest tremor + rigidity → nigrostriatal dopamine deficiency → Parkinson’s disease is likely.

Clinical Hook 2 — Cerebellar Ataxia

Broad-based gait + intention tremor + dysmetria → impaired cerebellar coordination → investigate the underlying cause.

Clinical Hook 3 — Huntington’s Disease

Progressive chorea + behavioral changes + affected parent → autosomal dominant Huntington’s disease → genetic counselling and multidisciplinary care.

Clinical Hook 4 — Acute Dystonia

Haloperidol or metoclopramide exposure + painful neck twisting or oculogyric crisis → acute dystonia → assess airway and provide anticholinergic treatment.

6. Starred High-Yield Exam Points

⭐ Parkinsonism: Bradykinesia + resting tremor or rigidity is the essential diagnostic combination.

⭐ Parkinson’s pathology: Substantia nigra dopamine depletion produces impaired movement initiation; Lewy bodies contain alpha-synuclein.

⭐ Levodopa pharmacology: Carbidopa inhibits peripheral levodopa conversion; long-term levodopa treatment can produce dyskinesia and motor fluctuations.

⭐ Cerebellar examination: Dysmetria, intention tremor and dysdiadochokinesia suggest cerebellar dysfunction, while sensory ataxia worsens markedly on eye closure.

⭐ Huntington’s disease: Autosomal dominant CAG repeat expansion in the HTT gene causes progressive chorea with cognitive and psychiatric manifestations.

⭐ Acute dystonia: Dopamine-blocking drugs may cause torticollis or oculogyric crisis; parenteral anticholinergic treatment is effective, while stridor indicates an airway emergency.