Peripheral nervous system conditions

Peripheral nerve injuries

Injuries to the peripheral nerves due to trauma, chronic traction, compression, or shear.

Definitions

Wallerian degeneration

Degeneration of the axon and myelin sheath distal to the site of an axonal interruption.

Neuropathy

Degenerative changes in peripheral nerves that produce loss of motor and sensory function; caused by diabetes, nutritional deficits, or alcohol use.

Mononeuropathy

Degeneration of a single nerve.

Polyneuropathy

Bilateral, symmetrical involvement of peripheral nerves, typically in stocking/glove distribution.

Entrapment syndrome

Pressure on a nerve where it passes through an opening or over a bony prominence.

Peripheral nerve injuries range in severity from a temporary compression injury to complete severance:

Type	Cause	Recovery
Neuropraxia	Compression injury	Reverses rapidly or persists for weeks; no surgery needed
Axonotmesis	Crush injury; axon interrupted, causing distal degeneration	Possible, with or without surgical intervention
Neurotmesis	Complete severance of the nerve	Fails without surgical intervention

Example: identifying a nerve injury type

A patient’s ulnar nerve is crushed but not severed. Motor and sensory function are absent distal to the injury, and the nerve is expected to regenerate over months without further surgery. Which type of injury is this?

Answer: Axonotmesis - the axon is interrupted and degenerates distally (a crush injury), but it can regenerate without surgery, unlike neurotmesis.

Myasthenia gravis

Definitions

Myasthenia gravis

An autoimmune disorder leading to decreased acetylcholine receptors at the neuromuscular junction, and thus a decrease in muscular contraction with repetition.

Symptoms

• Muscle weakness, especially in the eyes, face, throat, and limbs
• Double vision
• Drooping eyelids
• Difficulty swallowing or speaking
• Weakness that worsens with activity and improves with rest

Definitions

Myasthenia crisis

Occurs when the exacerbation of symptoms progresses to the respiratory system, leading to life-threatening weakness.

Tests and measures: manual muscle testing before and after repetition documents MG’s fatigue pattern; monitor respiratory and swallowing status for signs of crisis.

Interventions for myasthenia gravis

• Energy conservation techniques are the goal of the sessions
  • Avoid exercising to fatigue, because weakness worsens with repeated activity; when the disease is stable, low- to moderate-intensity strengthening and aerobic exercise with rest breaks is safe and can improve strength
• Attempt to conduct therapy sessions in the morning to decrease fatigue
• Avoid thermal modalities such as heat packs, whirlpool, etc.

PTA role: if fatigue increases with repetition, or signs of myasthenic crisis appear (sudden weakness, new difficulty breathing or swallowing), stop and report to the supervising PT rather than progressing the plan of care.

Bell’s palsy

Definitions

Bell’s palsy

A lower motor neuron lesion involving cranial nerve VII (facial nerve), causing unilateral facial paralysis due to acute inflammation of unknown etiology, resulting in compression of the nerve in the temporal bone.

Symptoms peak within the first few hours or days and typically last for several weeks to months.

Symptoms

• Facial droop on one side of the face
• Drooling from one side
• Loss of taste to the anterior 2/3 of the tongue
• Changes in saliva and tear production
• Headache
• Sensory to face remains intact

Tests and measures: grade facial muscle function with a standardized scale (e.g., House-Brackmann) to track recovery.

Interventions for Bell’s palsy

• Spontaneous recovery can occur
• Corticosteroid use for inflammation
• Electrical stimulation for nerve stimulation
• Exercises for facial muscles
• Taping of the eyelid to prevent dry eye due to the inability to close the eyelid

Guillain-Barré syndrome (GBS)

Definitions

Guillain-Barré syndrome (GBS)

An acute autoimmune disorder in which the myelin sheath of peripheral nerves is damaged. It typically occurs after recovery from a viral illness, causing demyelination of both cranial and peripheral nerves.

Symptoms

• Causes motor and mild sensory loss distal to proximal in a symmetrical pattern
• Usually begins in the legs and will ascend towards the trunk and upper extremities (UE)
• Worse prognosis if the disease progresses to the lungs, requiring mechanical ventilation
• Motor/sensory loss progressively worsens over a 4-week period and then stabilizes

Tests and measures: MMT and functional mobility measures track weakness progression; monitor vital capacity during the ascending phase.

Interventions for Guillain-Barré syndrome (GBS)

• Sessions focus on compensatory strategies to assist with gait and mobility
• Avoidance of overstretching and overuse during acute phases of diagnosis
• Strength training is performed once stabilization of the disease process occurs, with progression from isometric to concentric to eccentric activities

PTA role: if weakness or fatigue worsens with activity, or ascending weakness reaches respiratory muscles, stop and report to the supervising PT rather than progressing the plan of care.

Comparing myasthenia gravis, Bell’s palsy, and GBS

These three conditions overlap in that each produces weakness, but they differ in the pattern of that weakness and, critically, in how therapy is progressed. Lining them up side by side keeps the management distinctions from blurring together.