Peripheral Nerve Disorders/Nerve Injury Classification. NPTE Study Guide: Master the NPTE

What’s the etiology of a peripheral nerve injury?

Acute traumatic injury or chronic repetitive trauma d/t compression and/or shear forces

What’s Neuropraxia?

A nerve injury that causes a transient and focal loss of function (sensory or motor).

Nerve dysfunction can be rapidly reversed or persist for weeks to months.

It’s the mildest form of nerve injury d/t no nerve degeneration.

What’s Neuropraxia often related to?

Compressive forces causing ischemia (eg, carpal tunnel syndrome)

Positive/favorable Neuropraxia prognosis is indicated if…

If compression is removed

What’s Axonotmesis?

Focal damage to axon & myelin & varying degree of peripheral nerve connective tissue (endoneurium, perineurium, epineurium)

What’s Axonotmesis often related to?

Increased-duration & larger-amplitude compressive (crush injury) or traction forces

Axonotmesis prognosis is dependent on what?

The degree of connective tissue damage. Axonal regrowth occurs at about 1-3 millimeters per day or 1 inch per month

What’s Neurotmesis?

Severing of axon & myelin & all connective tissue structures. There’s a complete loss of function. Will requires surgery

What’s axon regeneration?

The process where damaged axons attempt to regrow and repair themselves after injury

What’s remyelination?

The process of restoring the myelin sheath around axons to repair damage

True or False: Axons that undergo axon regeneration will remyelinate to pre-injury level

False. Axons will not remyelinate to pre-injury level. This can impact the speed at which an electrical impulse travels along a nerve, as well as speed and coordination of bodily movement

What’s collateral sprouting?

The process where neighboring axons grow new branches to compensate for damaged axons, aiding in nerve regeneration

True or False: Intact axons can pick up denervated muscles

True. This often results in switching of muscle fiber type from type 1 to type 2

What’s Mononeuropathy?

A peripheral nerve injury involving a single nerve (eg, carpal tunnel syndrome)

What’s Mononeuropathy multiplex?

A peripheral nerve injury involving 2 or more nerves w/o a clear pattern of polyneuropathy. Presentation is often related to other health conditions (eg, diabetes mellitus, renal disease, chronic alcoholism)

What’s Radiculopathy

A peripheral nerve injury involving nerve root(s) being compressed or irritated

What’s Plexopathy

A peripheral nerve injury involving the brachial or lumbosacral plexus

What are the risk factors for Plexopathy?

DM, renal failure, alcohol abuse

Systemic autoimmune disease. Examples: Sjögren syndrome (dry eyes or mouth), lupus

Autoimmune diseases. Example: GBS

Nutritional imbalances

Hereditary. Example: Charcot-Marie-Tooth disorder

Infections. Examples: hepatitis B or C, human immunodeficiency virus (HIV), Lyme disease

Cancers

Medications. Example: chemotherapy

Toxins. Examples: radiation, pesticides

Idiopathic onset. Occurs in approximately 25% of patients

What are the 3 steps in the pathological process of Plexopathy?

1. Segmental demyelination

2. Axonal degeneration

3. Myelin and axons impact

What’s Segmental demyelination?

A disease process that primarily impacts myelin. If treated, remyelination can occur (eg, GBS)

What’s Axonal degeneration?

A disease that impacts axons to a greater degree than myelin. Progresses from distal to proximal (eg, neuropathy secondary to alcohol abuse)

True or False: Most polyneuropathic conditions impact both myelin and axons

True. (eg, diabetic polyneuropathy). They’re more chronic in nature

Acute & rapidly progressing polyneuropathic conditions are typically related to what?

Toxins (poison) or autoimmune conditions

What’s examined during a nerve injury examination

Sensory, motor, & autonomic symptoms

Screen for autonomic dysfunction

Balance and fall risks

What are Sensory, motor, & autonomic symptoms?

Hair loss & vascular changes

What directional fashions do Sensory, motor, & autonomic symptoms occur?

Distal to proximal fashion

Why is it important to test both small and large neural fiber involvement?

Because impairment may vary.

Small neural fiber involvement = pain, temperature

Large neural fiber involvement = proprioception, kinesthesia

What’s examined during a screen for autonomic dysfunction?

Vasodilation and loss of vasomotor tone (dryness, warmth, edema, orthostatic hypotension)

What’s examined during a screen for balance and fall risks?

Balance difficulty with static posture; sensitive to eyes being closed and looking upward