What is hemiparesis?

Hemiparesis: Definition and Clinical Implications

Hemiparesis is defined as weakness or partial paralysis affecting one side of the body, typically involving the face, arm, and leg on the same side. It differs from hemiplegia, which refers to complete paralysis of one side of the body 1.

Etiology and Pathophysiology

Hemiparesis most commonly results from:

• Stroke: The most frequent cause, accounting for the majority of cases 2, 1
• Traumatic brain injury: Second most common cause 1
• Brain tumors
• Infections (encephalitis or brain abscess)
• Demyelinating diseases

The weakness occurs on the opposite (contralateral) side of the body from the brain lesion, due to the crossing of motor pathways in the brainstem 1, 3.

Clinical Presentation

Hemiparesis manifests as:

• Motor weakness on one side of the body
• Variable severity - from mild weakness to near-complete loss of movement
• Distribution patterns that may provide clues to lesion location:
  • Leg-predominant weakness often indicates anterior cerebral artery territory involvement 3
  • Arm-predominant weakness typically suggests middle cerebral artery territory involvement
  • Face, arm, and leg involvement often indicates internal capsule lesions 3

Anatomical Considerations

The location of the lesion determines the specific pattern of weakness:

• Cortical lesions: May cause more distal than proximal weakness and can be associated with other cortical signs
• Subcortical lesions (internal capsule): Often produce more uniform weakness
• Brainstem lesions: Can cause crossed findings (ipsilateral cranial nerve and contralateral body involvement) 3, 4

Associated Features

Hemiparesis is often accompanied by:

• Sensory changes: Numbness or altered sensation on the affected side 4
• Hyperreflexia: Increased deep tendon reflexes
• Positive Babinski sign: Upgoing toe on stimulation of the sole 2
• Spasticity: Increased muscle tone developing over time 2
• Hemiplegic shoulder pain: Common complication requiring proper positioning and management 2

Complications and Management

Common complications include:

• Contractures: Affecting 60% of patients with hemiparesis within the first year after stroke 2
• Falls: Due to impaired balance and mobility 2
• Pressure injuries: Due to immobility 2
• Shoulder pain: Particularly in the hemiplegic shoulder 2

Management approaches include:

• Early rehabilitation: Recommended at an intensity appropriate to benefit and tolerance 2
• Regular stretching: Daily stretching of hemiplegic limbs to prevent contractures 2
• Proper positioning: Especially of the hemiplegic shoulder in maximum external rotation for 30 minutes daily 2
• Orthotic devices: Such as ankle-foot orthoses to improve gait and prevent contractures 2
• Pain management: For associated shoulder pain and other discomfort 2

Prognosis

Recovery patterns vary based on:

• Lesion location: Cortical lesions involving the primary motor cortex often have poorer recovery than those sparing it 3
• Severity of initial deficit: More severe weakness generally has poorer prognosis
• Timing of rehabilitation: Early rehabilitation is associated with better outcomes 2

Differential Diagnosis

Important differentials include:

• Hemiplegia: Complete paralysis rather than weakness 1
• Todd's paralysis: Temporary weakness following seizures
• Alternating hemiplegia of childhood: Rare disorder with recurrent episodes of hemiplegia that can shift sides 5
• Conversion disorder: Weakness without corresponding neuroanatomical pattern

Hemiparesis represents a significant clinical finding that requires prompt evaluation to determine the underlying cause and initiate appropriate management to prevent complications and optimize functional recovery.