NPTE (week 1) Peripheral Nerve Disorders

Neuropraxia

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

-Often related to compressive forces causing ischemia (carpal tunnel syndrome)

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

-Positive prognosis if compression removed

-Mildest form of nerve injury; no nerve degeneration

(sunderland 1º)

Neuropraxia signs and symptoms

-pain

-no or minimal muscle wasting

-muscle weakness

-numbness

-proprioception affected

-recovery time: minutes to days

Axonotemesis

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

-seen with increased-duration and larger-amplitude compressive (crush injury) or

traction forces

-prognosis is related to degree of connective tissue damage

-Axonal regrowth occurs at about 1 to 3 mm/day or 1 in/month

(sunderland 2º and 3º)

Axonotmesis signs and symptoms

-pain

-muscle wasting evident

-complete motor, sensory and sympathetic lost

-sensation is restored before motor function

-recovery time: months (axon regenerates at rate of 1 in/month or 1 mm/day)

Neurotemesis

severing of axon and myelin and all connective tissue structures (prolonged compression or stretch causing infarction and necrosis)

-Complete loss of function; requires surgery

Neurotemesis signs and symptoms

-no pain (anesthesia)

-muscle wasting

-complete motor, sensory and sympathetic functions lost (gunshot or stab wounds, avulsion, rupture)

-recovery time: months and only with surgery

(sunderland 3º, 4º, and 5º)

Axonal regeneration

axons that undergo regeneration do NOT remyelinate to preinjury level

- this can impact nerve conduction velocity, as well as speed and coordination of movement

***important

What is collateral sprouting?

intact axons can pick up denervated terminal targets (muscles)

-Often results in switching of muscle fiber type (from type 1 to type 2)

Mononeuropathy

type of peripheral nerve injury that involves single nerve (ex carpal tunnel)

Mononeuropathy multiplex

involvement of 2 or more nerves without clear pattern of polyneuropathy

-example: Patient with B/L CTS, left cubital tunnel, and right tarsal tunnel; Presentation is often related to other health conditions (eg, diabetes mellitus

[DM], renal disease, chronic alcoholism)

Radiculopathy

involvement of nerve roots

Plexopathy

involvement of brachial or lumbosacral plexus

Polyneuropathy risk factors

-DM, renal failure, alcohol abuse

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

-Autoimmune diseases (guillain barre syndrome)

-Nutritional imbalances

-Hereditary (Charcot-Marie-Tooth disorder)

-Infections (hepatitis B or C, human immunodeficiency virus (HIV), Lyme disease)

-Cancers

- Medications (chemotherapy)

-Toxins (radiation, pesticides)

-Idiopathic onset (Occurs in approximately 25% of patients)

What is axonal degeneration?

disease that impacts axons to a greater degree than myelin (progresses from distal to proximal) ex: neuropathy secondary to alcohol abuse

Most polyneuropathic conditions impact both __________ & _______

myelin and axons (ex diabetic polyneuropathy)

Sensory, motor and autonomic symptoms occur in what fashion?

Sensory, motor, and autonomic symptoms (hair loss and vascular changes) occur in

distal to proximal fashion (gloves and stocking)

How do you screen for autonomic dysfunction?

vasodilation and loss of vasomotor tone (dryness,

warmth, edema, orthostatic hypotension)

Balance and fall risks associated with peripheral nerve disorders

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

upward