Q4 · 20 Marks · Green
Spasticity vs Rigidity
Exam Question: Explain the difference between spasticity and rigidity in upper motor neuron lesions. Include clinical examples, presentations and tests in your answer.
§1 Anatomy3 marks
§2 UMN Features4 marks
§3 Spasticity3 marks
§4 Rigidity3 marks
§5 Examples3 marks
§6 Tests2 marks
UMN/LMN Table+bonus
⚡ Spasticity
- Speed-dependent resistance
- Clasp-knife phenomenon
- Hyperreflexia
- Babinski positive
- Corticospinal / UMN tract
🔩 Rigidity
- Regardless of speed
- Lead-pipe uniform resistance
- Cogwheel (tremor superimposed)
- Normal reflexes, no Babinski
- Extrapyramidal / Parkinson's
⚠️ Clinical Distinction — Important for Full Marks
ICOM slides list clonus and cogwheel together under UMN features. Clinically, cogwheel rigidity belongs to extrapyramidal (Parkinsonian) pathology — not true UMN. Distinguish clearly in your answer: spasticity = corticospinal; cogwheel rigidity = basal ganglia. Examiners reward this nuance.
§1 UMN & LMN Anatomy 3 marks
Upper Motor Neuron (UMN) pathway:
Motor Cortex→
Subcortical Fibres→
Internal Capsule→
Brainstem→
Corticospinal Tract→
Anterior Horn Cell
Lower Motor Neuron (LMN) pathway:
Anterior Horn Cell→
Nerve Root→
Peripheral Nerve→
NMJ→
Muscle
UMN lesions affect the corticospinal tract above the anterior horn. LMN lesions affect the final common pathway from the anterior horn to muscle. This anatomical distinction explains the contrasting clinical signs.
Ref: ICOM UMN v LMN pptx, Year 4 Google Classroom
§2 UMN Clinical Features 4 marks
Tone
Initially flaccid (spinal shock), then spasticity develops over hours–days. Catch in pronators on passive supination; catch in wrist extensors.
Clasp-Knife
Initial resistance to passive movement then sudden release — like a penknife closing. Velocity-dependent.
Clonus
Rhythmic contractions after sustained stretch (e.g. ankle). >3 beats = pathological UMN sign.
Weakness Pattern
Pyramidal pattern — muscle groups not individual muscles. Anti-gravity muscles: flexors UL, extensors LL.
Reflexes
Hyperreflexia (brisk DTRs). Extensor plantar response (Babinski positive). No wasting, no fasciculations.
Gait
Hemiplegic circumduction gait. Arm flexed, pronated. Leg extended, adducted, circumducted.
Ref: ICOM UMN v LMN pptx, Year 4 Google Classroom
§3 Define Spasticity 3 marks
Definition: A velocity-dependent increase in tonic stretch reflexes, resulting from UMN (corticospinal tract) lesion. Resistance to passive movement increases with speed.
- Velocity-dependent: Move limb slowly → less resistance; move quickly → marked resistance
- Clasp-knife phenomenon: Initial resistance then sudden release at end of range
- Hyperreflexia: Brisk deep tendon reflexes (DTR grade 3–4)
- Clonus: Rhythmic oscillations on sustained stretch (>3 beats pathological)
- Babinski positive: Extensor plantar response — hallmark UMN sign
- Pyramidal pattern weakness: Flexors UL, extensors LL preferentially affected
- Lesion site: Corticospinal tract — motor cortex → anterior horn
Ref: ICOM UMN v LMN pptx; Kumar P & Clark M, Clinical Medicine 10th ed, Elsevier 2021
§4 Define Rigidity 3 marks
Definition: A velocity-independent increase in muscle tone — constant resistance throughout the full range of passive movement, regardless of speed. Extrapyramidal (basal ganglia) pathology.
- Lead-pipe rigidity: Uniform, constant resistance throughout range — no clasp-knife release
- Cogwheel rigidity: Ratchet-like, jerky resistance — tremor superimposed on lead-pipe (Parkinson's)
- Velocity-independent: Same resistance whether moved slowly or quickly
- Lesion site: Extrapyramidal — basal ganglia pathology
- Parkinson's disease: Dopamine deficiency (substantia nigra) → relative acetylcholine excess (corpus striatum)
- Parkinsonian triad: Rest tremor · Bradykinesia · Rigidity
- Normal reflexes: DTRs normal; Babinski negative — distinguishes from spasticity
Ref: ICOM UMN v LMN pptx; NICE NG71 Parkinson's Disease in Adults 2017 (updated 2023)
§5 Clinical Examples 3 marks
| Condition | Tone Type | Key Features |
|---|---|---|
| Stroke (right hemisphere) | Spasticity | Left arm flexed/pronated, left leg extended/adducted; dysphasia (dominant); sensory disturbance; hemiplegic gait |
| Brainstem lesion | Spasticity (all 4 limbs) | Spastic quadriparesis + cranial nerve involvement: diplopia, vertigo, dysphagia, dysarthria |
| Cervical myelopathy | UMN below level; LMN at level | Bilateral hand tingling/weakness (LMN at level), spastic legs (UMN below), bladder/bowel dysfunction, Lhermitte sign |
| Multiple Sclerosis | Spasticity | Relapsing-remitting; optic neuritis; cerebellar signs; UMN signs; fatigue; Lhermitte sign |
| Parkinson's Disease | Cogwheel rigidity | Extrapyramidal; rest tremor (pill-rolling); bradykinesia; festinant shuffling gait; hypomimia; micrographia |
Ref: ICOM UMN v LMN pptx; ICOM Vascular and Neurology ppt, Year 4 Google Classroom
§6 Clinical Tests 2 marks
| Test | Method | UMN Positive Finding |
|---|---|---|
| Tone Assessment | Passive movement slow then fast at wrist, elbow, knee, ankle | Spasticity: velocity-dependent catch; Rigidity: constant resistance |
| DTR Grading | Tendon hammer: biceps C5/6, triceps C7, knee L3/4, ankle S1 | Grade 3 (brisk) or 4 (clonus) = UMN; Grade 0–1 = LMN |
| Babinski Sign | Stroke lateral sole heel to ball with orange stick | Extensor plantar (big toe up, fan) = UMN positive |
| Clonus | Rapid ankle dorsiflex, sustain pressure | >3 beats sustained clonus = pathological UMN |
| Hoffmann Sign | Flick middle fingernail downward; observe thumb/index | Thumb/index flexion = UMN upper limb equivalent of Babinski |
| Power (MRC 0–5) | Test muscle groups in pyramidal pattern | Weakness: flexors UL, extensors LL (pyramidal distribution) |
| Gait Observation | Walk 10 metres, turn, return | Hemiplegic circumduction (UMN); shuffling festinant (Parkinson's) |
Ref: ICOM UMN v LMN pptx; ICOM Cervical and Thoracic Spine Assessment, Year 4
§ UMN vs LMN Comparison Table Key Table
| Feature | UMN Lesion | LMN Lesion |
|---|---|---|
| Tone | Increased (spasticity) | Decreased (flaccidity) |
| Weakness | Pyramidal groups (flexors UL, extensors LL) | Individual muscles (myotomal) |
| Wasting | Disuse only (slow) | Rapid — 2–3 weeks |
| Fasciculations | Absent | Present |
| Reflexes | Hyperreflexia (brisk) | Reduced or absent |
| Plantar Response | Extensor (Babinski +ve) | Flexor (normal) |
| Clonus | Present | Absent |
| Hoffmann | Positive | Negative |
| Clinical Examples | Stroke, MS, myelopathy, brainstem lesion | Disc prolapse, peripheral neuropathy, MND (LMN) |
Ref: ICOM UMN v LMN pptx, Year 4 Google Classroom
🦴 Osteopathic Safety — UMN Lesions
- New UMN signs = medical emergency: Refer immediately — do not treat until cause established
- Cervical myelopathy must be excluded before any cervical manipulation — bilateral hand tingling, gait disturbance, hyperreflexia, Babinski, Hoffmann
- RA atlantoaxial subluxation in 30–40% of RA patients — transverse ligament/odontoid erosion — cervical HVLA absolutely contraindicated unless instability excluded by imaging
- Screen for myelopathy: Bilateral hand tingling · Gait disturbance · Hyperreflexia · Babinski · Hoffmann · Bladder/bowel dysfunction · Lhermitte sign
- Document neurological baseline before and after any treatment — essential for medico-legal safety
- Parkinson's patients: Postural instability — fall risk during examination and treatment; adjust positioning accordingly
Ref: ICOM Manipulation Notes Summary; ICOM Cervical and Thoracic Spine Assessment, Year 4
🚩 Red Flags — Refer Immediately
- Bilateral hand tingling or weakness (myelopathy until proven otherwise)
- Gait disturbance with upper limb neurological signs
- Hyperreflexia + extensor plantar (Babinski positive)
- Bladder or bowel dysfunction with limb signs (cauda equina / myelopathy)
- Sudden onset neurological deficit — stroke protocol
- Progressive neurological deterioration
- Lhermitte sign (electric shock down spine on neck flexion)
- Dysphagia, diplopia, dysarthria with limb signs (brainstem)
- New UMN signs in known RA patient — atlantoaxial emergency
📚 References
- ICOM UMN v LMN pptx — Year 4 Google Classroom
- ICOM Manipulation Notes Summary — Year 4 Google Classroom
- ICOM Cervical and Thoracic Spine Assessment — Year 4 Google Classroom
- ICOM Vascular and Neurology ppt — Year 4 Google Classroom
- Kumar P & Clark M. Kumar & Clark's Clinical Medicine, 10th ed. Elsevier, 2021
- Snell RS. Clinical Neuroanatomy, 7th ed. Lippincott Williams & Wilkins, 2010
- NICE NG71. Parkinson's Disease in Adults. 2017 (updated 2023)