Features of Contralateral Hemiplegia

1. Motor Weakness

• Contralateral arm and leg are affected; movements are lost as groups rather than as individual muscles.
• The arm is typically more severely affected than the leg when the lesion is above the level of the facial nucleus (internal capsule, corona radiata, motor cortex).
• Bilateral movements (eyes, jaw, pharynx, upper face, neck, diaphragm) are spared because these muscles have bilateral cortical representation.
• UMN paralysis is rarely complete for a prolonged period - partial recovery is the rule.

2. Facial Involvement - Lower Face Only (Broadbent's Law)

3. Tone - Spasticity

• Spasticity develops, characterized by velocity-dependent increase in muscle tone (resistance increases with faster passive stretch).
• The "clasp-knife" phenomenon: on rapid passive stretch, there is an initial free movement followed by a catch, then sudden release of resistance.
• Antigravity muscles are predominantly affected: flexors of the arm and extensors of the leg - so the arm tends to be flexed and pronated, the leg extended and adducted.
• Spasticity results from loss of cortical inhibition over the reticulospinal and vestibulospinal tracts.
• Note: acutely, there may be initial flaccidity (especially with spinal cord lesions - "spinal shock"), which evolves into spasticity over days to weeks.

4. Reflexes

• Exaggerated (hyperactive) deep tendon reflexes contralaterally - a "release" phenomenon from loss of descending inhibitory pathways.
• Clonus: rhythmic involuntary muscle contractions (5-7 Hz) in response to sustained stretch, typically at ankle or patella.
• Hoffman's sign: positive on the affected side (flicking the middle fingernail causes thumb flexion).
• Crossed adductor reflex may be present.
• Abdominal and cremasteric superficial reflexes are absent on the affected side.
• Spread of reflexes (radiation): tapping one tendon elicits reflex contractions in distant muscles.

5. Babinski Sign (Plantar Response)

• Extensor plantar response (Babinski sign) is positive on the affected side: stroking the lateral plantar surface of the foot causes extension of the great toe and fanning of other toes - the most reliable indicator of UMN involvement.
• This represents disinhibition of the spinal flexion/protective reflex program.

6. Posture

• Upper limb: flexed at elbow, wrist, and fingers; forearm pronated.
• Lower limb: extended at knee and hip; foot plantar-flexed and inverted (equinovarus).
• This constitutes the classic Wernicke-Mann posture (also called hemiplegic posture).

7. Gait - Circumduction (Hemiplegic Gait)

• The patient holds the affected leg stiffly, unable to flex freely at hip, knee, and ankle.
• The leg rotates outward to describe a semicircle (circumduction) - first away from then toward the trunk.
• The foot scrapes the floor (toe and outer heel contact), producing the characteristic scuffing sound.
• The affected arm is carried in a flexed position and does not swing naturally.
• In hemiparetic children, the arm tends to abduct as they step forward.
• - Adams and Victor's Principles of Neurology, 12th Edition

8. Associated Movements

• Attempted flexion of the affected arm may produce involuntary pronation, flexion of the leg, or dorsiflexion of the foot.
• Volitional movement of the paretic limb may evoke mirror (imitative) movements in the normal limb.
• Some patients recovering from hemiplegia develop movement disorders (tremor, athetosis, chorea) on the affected side - due to associated basal ganglionic/thalamic damage.

9. Involvement of Specific Muscles

• Movements invariably bilateral (eyes, jaw, pharynx, larynx, thorax, diaphragm, abdomen) are not significantly affected - due to bilateral innervation.
• The trapezius on the hemiplegic side may be paretic; notably the head turns away from the hemiplegic side (indicating paresis of contralateral sternocleidomastoid).

10. Acute vs. Chronic Phase

Crossed (Alternating) Syndromes - Brainstem Lesions

• Adams and Victor's Principles of Neurology, 12th Edition - pp. 72-74
• Localization in Clinical Neurology, 8th Edition - Brainstem and Cranial Nerve sections
• Harrison's Principles of Internal Medicine, 22E (2025) - Signs and Symptoms table