Peripheral Neuropathies

PNS

Organization

Bundles of axons running to and from the CNS

Motor Axons; Single axons stretch from anterior horn to NMJ

Sensory Axons: Single axons stretch from receptors to central sensory pathways via pseudo-unipolar dorsal root ganglion

Anatomy

Individual nerve trunks made up of many nerve fasicles which in turn are composed of axons

Myelination

Speed up conduction in order to conduct faster than unmyelinated fibers due to saltatory conduction

CNS and PNS

Oligodendrocytes: Myelinating glial cells, direction of myelination centripetal, and Several per cell

Schwann cells: Centrifugal and one per cell

Physiology of Function

nerve fiber and diameter correlate with function (Large myelin - Spindle, Golgi, Sensory, Motor, Small/Inter - Touch, hair, pain, motor, Unmyelin - Temp, pain (slow sympathetic)

Symptoms of Neuromuscular Disease

Motor Symptoms (weakness)

Sensory symptoms (Numbness, tingling, burning)

Neurogenic Process: Atrophy, fasciculations, normal/hypotonic tone, diminished reflex, weakness pattern

Myopathic Process: Little/no atrophy, normal tone, normal reflexes

NMJ: No sensory symptoms, weakness variable

Sensory Exam

Pattern is anatomic based on nerve/root distribution

Amyotrophic Lateral Scleoriss

Description

Clinical Diagnossis based on UMN, and LMN Signs

Absence of significant sensory abnormalities

Bulbar Symptoms (Dysphagia, speech abnormalities)

Pseudobulbar affect (emotional incontinence)

Denervation on EMG

Degenerative Disc Disease

Commonest cause of isolated radiculopathy, cervical, thorcic, lumbar, sacral, radicular pain, numbness/paresthesia in dermatome of nerve root, loss of strength in myotome

Plexopathies

Brachial Plexopathies

Traumatic: Following shoulder disclocation

Malignant: With apical lung cancer, painful, lower trunk, associated with horner's syndrome

Diabetic Lumbosacral Plexopathies

Inflammatory: Brachial Plexitis, neuralgic amyotrophy, parsonage-Turner Syndrome

Abrubt onset of unilateral leg pain, weakness follows pain

Believed to be ischemic, often good recovery but residual weakness

Mono neuropathies

Median Nerve at Wrist: Carpal Tunnel

Ulnar at Elbow: Ulnar claw

Radial at Spiral Groove: Saturday night palsy -> Wrist drop

Lateral Femoral Cutaneous : Meralgia paresthetica

Peroneal at fibular head: Foot drop, steppage gait

Polyneuropathies

Classification Methods

Type of Nerve involved: Sensory, motor, sensorimotor, autonomic, generalized

Mechanism of Damage: Axonal, demyelinating, Mixed

Distribution: Length-dependent, mononeuritis multiplex

Time Course: Acute, subacute, chronic

Approach to Neuropathies

Typical

Chronic, sensorimotor, axonal, length dependent (diabetes)

Others: Toxic, Alcoholic, B12 deficiency, uremic, thyroid

Atypical

Mononeuritis multiplex: Vasculitis

Pure Motor: Lead

Pure sensory: Paraneoplastic, Platinum derived Chemo

Hereditary: Charcot marie tooth

Acquired demyelinating: GBS

Polyneuropathy

Motor symptoms: Weakness, loss of muscle bulk, cramps

Sensory symptoms: Numbness, loss of feeling, tingling, burning, pain, poor balance, autonomic symptoms

Nerve Conudction Study

Determine which nerve is involved

Determine sensory/motor, small vs large fiber, axonal vs demyelinating, acute vs chronic

Diabetic Neuropathy

Most diabetics will have some neuropathy after 10 years

Seneveral Clinnical Patters

Distal tingling/numbness

Small fibre predominant (burning dysesthetic pain)

Large fibre predominant (very little/no pain, prominent ataxia)

Autonomic Neuropathy

Resting Tachycarida, loss of sinus arrhythmia, postural hypotension, erectile dysfunction/impotence, bladder dysfunction, swearing/pupillary abnormaltiies

Diabetic 3rd nerve palsy

Ptosis, diplopia, Spares pupil

Guillain Barre Syndrom

Description

Acute inflammatory demyelinating polyradiculoneuropathy

Autoimmune attach on myelin sheaths

Clinical Features

Acute illness developing over few days-weeeks

Tingling paresthesia and pain are often the first symptoms

Dominant Feature is weakness (aschending paralysis is a bad term but legs before arms)

Symetric, faicla fweakness, and resp failure

Diagnosis

Primarily clinical diagnosis, nerve conduction study (often normal or minimally non sepcific), lumbar puncture (CSF protein elevated and albuminocytologic dissociation)

Pathophysiology

Loss of myelin sheath leading to slowed conduction velocity or conudctiion block

Treatment

Immunomodulatory, supportive therapy

IVIg Intravenous

Plasmapheresis

Initiate treatment quickly

General Management

Close monitorying of respiratory status (Bedisde spirometry) autonomic instability, DVT prophylaxis, Stress ulcer, Nosocomial infections, Bowel routine, urinary catheter, swallowing issues, pain control, SIADH