Neurology JC023: Unsteady Gait: Cerebellar Lesions, Movement Disorders, Parkinsonism Flashcards
Physiology of gait
3 levels of gait control:
1. Upper level (**Gait execution)
- Premotor cortex
- Motor cortex
- Regulatory system: **Extrapyramidal system (e.g. Basal ganglia)
- Middle level (Subcortical centres: **Synergy of gait)
- Midbrain locomotor region (MLR)
- Spinal locomotor network (SLN)
- Regulatory system: **Cerebellar system - Lower level (Force production)
- Peripheral nervous system
- Musculoskeletal system
- Regulatory system: Spinal reflex pathways (Vestibular + ***Proprioceptive inputs)
Regulatory system: **Postural control + **Balance
Gait disorders
- Apraxic gait
- **Motor cortex + Extrapyramidal system affected (Diffuse problem)
- **Difficulty initiating walking, 行行下唔行 - Parkinsonian gait
- ***Extrapyramidal system affected
- Hypokinetic gait, Small steps, Turn slowly - Ataxic gait
- **Cerebellar system + Spinal reflex pathways affected
- **Wide based, Truncal unsteadiness - Hemiplegic / Diplegic / Spastic gait
- Upper level of gait centre affected (e.g. Stroke) - Antalgic gait
- Musculoskeletal system affected (∵ pain) - Waddling gait
- Musculoskeletal system affected
Causes of Gait disorders
- Motor deficits
- UMN (spasticity)
- LMN (amytrophy = muscular wasting)
- Muscular disorders - Movement disorders (Extrapyramidal disease)
- Sensory ataxia
- Cerebellar ataxia
- Vestibular disorders
- Parkinsonian syndromes
- Normo-pressure hydrocephalus
Revision: Cerebellum
Cerebellum:
- Coordination / Fine-tuning of voluntary movements
- Control of equilibrium + muscle tone
- Responsible for ***ipsilateral side
Vermis / Other paramedian structures:
- **Truncal stability
- **Gaze fixation
- ***Gait
—> rely on integration of Sensory (Vision) + Vestibular + Motor (Proprioception) signals input
Cerebellar disorders
Ataxia (共濟失調症):
- ***loss of coordination
- irregularity / disorderliness
- may result from:
1. Cerebellar disorders
2. Impaired sensory feedback (Sensory ataxia)
- Limb ataxia / Ataxic gait
- Dysmetria + Tremor + Dysdiadochokinesia
- hard to test if weakness / sensory impairment
- muscle tone is reduced but often not apparent - Scanning dysarthria (***specific for cerebellar disorder)
- Explosive dysarthria (incoordination of speech / respiration —> speech volume / rate vary from word to word) + Cerebellar speech (slow + slurred) - Nystagmus
- vestibulocerebellar pathway affected —> Ocular Dysmetria (jerkiness of smooth-pursuit eye-movements with disrupted fixation)
- **Gaze-evoked + **Horizontal
- unilateral lesion: fast-phase of nystagmus is towards the ***affected side - Dysmetria
- errors in range + force of movements —> under / over-shooting of target: Finger-nose, Heel-shin test - Dysdiadochokinesia
- decomposition of fine repetitive movements
- NOT specific for cerebellar disorders
- can be seen in ALL neurological conditions affecting motor control of limb - Hypotonia
- Intention / Kinetic tremor
- exaggerated by maximising range of movement tested - ***Pendular tendon reflexes
Etiologies of Cerebellar disorders
Children:
- Congenital maldevelopment (Arnold-Chiari malformation, Dandy-Walker syndrome)
- Metabolic disorders
- **Infections (Chicken pox encephalitis)
- **Tumours (Medulloblastoma, Cystic astrocytoma)
- Hereditary degenerative disorders
Adult:
- Hereditary degenerative disorders (AD Spinocerebellar ataxias, Recessive Friedreich’s ataxia)
- Alcoholism
- **Cerebrovascular disease
- **Multiple sclerosis
- **Metabolic disorders (e.g. Hypothyroidism)
- **Drug overdose (e.g. Anticonvulsant, Antihistamine)
- ***Tumours (direct involvement / paraneoplastic syndrome)
Ataxic gait
Result of Incoordination of movements + Unsteady balance of trunk
Features:
- **Wide based (to maintain balance)
- **Truncal unsteadiness (when asked to walk tandem)
- **Tendency to Jerk sideway
- **Walk relatively quickly
- Irregular length / synergy
- Greatly exacerbated during rapid postural adjustments e.g. Turning corners
- may combine with other gait disorders (e.g. Spastic gait in MS, High-stepping gait in Tabes dorsalis)
Hemiplegic gait
- Arm adducted
- Internally rotated at shoulder
- ***Flexed at elbow
- Pronation of forearm
- ***Flexion of wrist and fingers
- Leg slightly flexed at hip
- ***Extended at knee
- Plantar flexion
- ***Inversion at foot
Apraxic gait / Gait apraxia
- ***Difficulty initiating walking
- Disorganised walking skills
- ***Shuffling small steps
- BUT ***arm swing and posture are normal (vs PD: reduced arm swing, stooping posture)
Cerebellum vs Basal ganglia
Cerebellum: Rapid (ballistic movement)
Basal ganglia: Slow (ramp, smooth movement)
1. Caudate nucleus
2. Putamen
3. Globus pallidum
4. Substantia nigra
Extrapyramidal disorders (aka Movement disorders)
Disorders of Basal ganglia:
- affect slow (ramp) rather than rapid (ballistic) movements
Basal ganglia motor loop:
- complex network consisting of multiple nuclei
- D1: excitatory pathway
- D2: inhibition pathway
- normally balance out each other, imbalance: Movement disorders
Dyskinesia / Hyperkinetic disorders (Defect in D2 inhibition pathway)
- Chorea (舞蹈症)
- Ballismus (芭蕾舞症)
- Athetosis (手足徐動症), Choreoathetosis
- Dystonia (肌張力不全症)
- Tremor (顫抖症)
- Myoclonus (肌躍症)
- Tics (肌抽搐症)
Akinesia / Hypokinetic disorders (Defect in D1 excitatory pathway)
- Parkinsonism
Chorea (舞蹈症)
Lesion in Striatum / related structures
Features:
- **Irregularity + **Randomness + Excessive + **Spontaneous + Jerky + Non-repetitive
- At different parts of body in random sequence
- **No weakness
- Gait: Tendency to sway + jerk
- ***Muscle tone ↓
- Patient may mask it by Quasi-purposive (seemingly on purpose)
- Irregular + Explosive speech
Causes:
- Huntington’s disease
- Cerebral palsy
- **Kernicterus (excessive bilirubin)
- Rheumatic fever (Sydenham’s chorea, reactivate as **Chorea gravidarum during pregnancy)
- SLE
- Structural lesions (e.g. Tumour, AV malformation)
- ***Wilson’s disease
(- Can be secondary to PD due to high Levodopa dose)
Hemiballismus (單側芭蕾舞症) / Ballismus (芭蕾舞症)
Exaggerated form of Chorea / Proximal chorea
Etiology:
- Stroke —> Lesion affect **Contralateral Basal ganglia / Subthalamic nucleus unilaterally —> **Contralateral Hemiballismus
Features:
- Irregular, Non-repetitive
- ***Violent excursions of affected limbs (∵ proximal muscles affected)
Treatment:
- ***Tetrabenazine (block Dopamine reuptake)
Prognosis:
- usually disappear several weeks after onset
Athetosis (手足徐動症)
Etiology:
- **Neonatal cerebral hypoxia
- **Kernicterus
Features:
1. ***Abnormal limb posturing
- Shoulder: Adducted + Internally rotated
- Elbow: Semi-flexed
- Wrist / MCP joints: Flexed
- IP joints: Extended
- ***Slow, coarse, twisting writhing movements of extremities
- Flexion / Extension of wrist, fingers, elbow
- Retraction, Internal rotation at shoulder - Patient may grasp affected limb with normal hand to ***restrain movement
- UMN signs may present
- Lower limb less affected
Dystonia (肌張力不全症)
Frozen Athetosis
***Abnormal posturing
Etiology (reversible):
- Focal brain lesion (involving Basal ganglia, Rostral midbrain)
- Wilson’s disease
- Drug-induced dystonia
Features:
- **Excessive muscular tone + contraction of antagonistic muscle groups
—> Sustained postural distortion of limbs + trunk (扭麻花, painful)
—> may be distorted by Repetitive spasmodic twisting movements
- **Posture / Action / Task-specific
- Sporadic / Familial
Types:
1. Focal Dystonia (more common)
- **Cervical dystonia (Spasmodic torticollis)
- **Blepharospasm
- Foot dystonia
- Writer’s cramp
- Generalised dystonia
Treatment:
- **Anticholinergics
- Levodopa
- **Benzodiazepines
- Botox local injection