Peripheral Nerve Disorders

Question 1

Peripheral Nerve Disorders

Subtypes

Answer 1

Peripheral nerve ⇒ neuropathy

Nerve root ⇒ radiculopathy

Lumbar or brachial plexus ⇒ plexopathy

Anterior horn ⇒ motor neuron disease

Question 2

Peripheral Nervous System

Basic Anatomy

Answer 2

• Consists of nerves and ganglia outside of the brain and spinal cord
• Peripheral nerves connected to spinal cord by two roots:
  
  • Ventral root ⇒ motor
  • Dorsal root ⇒ sensory
• Interconnects all other tissues with the CNS
• Innervates all voluntary muscles
• Transmits the sensory impulses to the whole body
• Individual nerve fibers ⇒ vary widely in diameter and may be heavily myelinated, lightly myelinated or unmyelinated
  
  • Amount of myelin ∝ conduction speed
• Largely under conscious (cerebral) control
• Injury results in both sensory and motor loss

Question 3

Sensory Innervation

Answer 3

• A sensory nerve (afferent nerve) carries sensory information toward the CNS
• It is a bundle of nerve fibers coming from sensory receptors in the PNS
• Afferent nerve fibers leave the sensory neuron from the dorsal root ganglia of the spinal cord
• Large myelinated sensory fibers ⇒ vibration and proprioception
• Small myelinated and unmyelinated sensory fibers ⇒ pain and temperature

Question 4

Motor Innervation

Answer 4

• Upper Motor Neuron
  
  • Neuron in the motor cortex
  • Travels down and decussates at the level of the medulla
  • Travels down the spinal cord
• Lower Motor Neuron
  
  • Neuron in the spinal cord or cranial nerve of brainstem
  • Travel to the skeletal muscle

Question 5

Motor Unit

Answer 5

A motor neuron and all the skeletal fibers it innervates.

• Groups of motor units work together to coordinate contraction of a single muscle
• It is a functional unit made up of:
  
  • Lower motor neuron
  • Motor axon
  • NMJs
  • Muscle fibers innervated by the motor neuron

Question 6

Upper Motor Neuron

Signs

Answer 6

• Weakness
• Hyperreflexia
• Spasticity
• Stiffness
• Babinski sign
• Brisk jaw jerk

Question 7

Lower Motor Neuron

Signs

Answer 7

• Fasciculations
• Atrophy/muscle wasting
• Weakness
• Muscle cramps
• Loss of reflexes

Question 8

Disease Localization

Answer 8

Differentiating PNS from CNS disease

• Weakness or sensory loss confined to one limb ⇒ peripheral nerve problem
  
  • Associated pain in the extremity ⇒ ↑ likelihood of a peripheral process
• Localization less obvious when weakness/sensory loss involves > 1 extremity or when there is no associated pain or discomfort
• The patient approach will include taking a detailed hx including family hx of similar sx, time course of sx, and comorbidities (ex. DM)
• Complete neurologic exam will be extremely helpful

Question 9

Peripheral Nerve

Composition

Answer 9

Peripheral nerve is composed of:

• Motor axon/neuron
• Sensory axon/neuron
• Autonomic fibers
• Myelin
• Other supporting structures

Question 10

Peripheral Nerve

Characteristics

Answer 10

• Individual nerve fibers ⇒ vary widely in diameter and may be heavily myelinated, lightly myelinated or unmyelinated
  
  • Amount of myelin ∝ conduction speed
  • Myelin made by Schwann cells
  • Distance b/t nodes of Ranvier determines conduction rate
• Largely under conscious (cerebral) control
• Injury results in both sensory and motor loss

Question 11

Peripheral Nerve Damage

Answer 11

• Segmental demyelination
  
  • Diseases primarily affect Schwann cells ⇒ loss of myelin
• Nerve injury/transection
  
  • Primary destruction of the axon ⇒ secondary disintegration of its myelin sheath
  • Results in axonal degeneration
    
    • Distal portion ⇒ Wallerian degeneration
    • Proximal portion ⇒ retrograde degeneration
    • Begins in the periphery and proceeds back toward the cell body ⇒ “dying back“
  • Cell body may become chromatolytic
  • If process reversed early phases, some regeneration may be possible

Question 12

Axonal Injury

Answer 12

Traumatic transection of a nerve

• Distal portion of the nerve fiber degenerates ⇒ Wallerian degeneration
  
  • Axons begin to break down
  • Schwann cells begin to catabolize myelin and later engulf axon fragments, forming myelin ovoids
  • MΦ recruited and phagocytose axonal and myelin-derived debris
• Proximal portion of severed nerve degenerates ⇒ retrograde degeneration
  
  • Degenerative changes involving only the most distal two or three internodes
  • Proximal stump then undergoes regenerative activity
  • Regenerated fiber has shorter internodes

Question 13

Segmental Demyelination

Answer 13

• Selective loss of individual myelin internodes with preservation of the axon
• Process affects some Schwann cells and their corresponding internodes while sparing others
• Disintegrating myelin is engulfed initially by Schwann cells and later by MΦ
• After segmental demyelination, Schwann cells can proliferate and remyelinate
• Example: Guillain-Barré Syndrome

Question 14

Regenerative Processes

Answer 14

• Axonal Sprouting
  
  • After axonal damage, the axon may sprout from the distal end
  • Regenerating axons re-grow at ~ 1 mm/day
• Remyelination stimulated by denuded axon
  
  • Segmentally demyelinated axons may remyelinate ⇒ shorter internodes = slower conduction
  • Axonal sprouts will be re-myelinated by surviving Schwann cells
  • Remyelination may restore some function
  • Repeated episodes of demyelination and remyelination → accumulation of layers of Schwann cell processes
    
    • Onion Bulb: a single thinly myelinated axon surrounded by concentrically arranged Schwann Cells and redundant BM

Question 15

Neurodiagnostic Testing

Answer 15

Electromyography (EMG) and Nerve conduction studies (NCS)

• Most common diagnostic tests for dx of nerve and muscle disease after hx and exam
• Both are complementary and are always performed together during the same setting

Question 16

Nerve Conduction Studies (NCS)

Answer 16

Measure the ability of sensory and motor fibers to conduct an action potential

Used mainly for eval of paresthesias and/or weakness of arms and legs

• Axonal injury/neuropathy
  
  • ↓ amplitude of AP
  • Mild slowing
  • Can see mix of both
• Demyelination neuropathy
  
  • Conduction block (failure of AP to propogate)
  • Slow conduction
  • Amplitude of AP may be normal or reduced

Question 17

Electromyography (EMG)

Answer 17

Measures muscle response or electrical activity in response to nerve stimulation of the muscle

Used to determine NMJ abnormalities, myopathy, and denervation

• Increased insertion activity
  
  • Denervation ⇒ will fire spontaneously as a “Fibrillation potential”
  • Polymyositis
• Decreased insertional activity
  
  • Myopathy ⇒ loss of response of motor units
    
    • Small motor units
    • Early recruitment of other motor units
    • Muscle is replaced by fat
• Muscle fibers s/p denervation and reinnervated ⇒ very large due to reorganization and formation of large motor units

Question 18

Peripheral Nerve Biopsy

Answer 18

• Used when the pathology is in question and when therapy is contemplated
• Superficial sensory branches of the sural or radial nerves are often sampled and examined pathologically

Question 19

Peripheral Neuropathy Patterns

Answer 19

Patterns of peripheral neuropathy aids in clinical dx and finding underlying pathologic processes:

• Mononeuropathy
• Mononeuropathy Multiplex
• Polyneuropathy

Question 20

Focal Neuropathies

(Mononeuropathies)

Answer 20

• Typically have damage to a single nerve
• Etiologic agents are focal ⇒ process tends to be asymmetric
• Classic cause is vasculitis ⇒ produces discrete infarctions in nerve trunks
• NO distal-proximal gradient b/c an individual nerve trunk is affected

Question 21

Median Nerve

Answer 21

Responsible for:

• Flexion of the thumb, index, and middle fingers
• Wrist flexion
• Thumb opposition
• Forearm protonation
• Hand abduction

Question 22

Median Nerve Entrapment

(Carpal Tunnel Syndrome)

Answer 22

Secondary to compression of the median nerve as it passes through the carpal tunnel

Most common nerve entrapment

• Due to any condition that causes decreased space within the carpal tunnel
  
  • Tissue edema, pregnancy, inflammatory arthritis, hypothyroidism, amyloidosis acromegaly, DM, and excessive repetitive motions of the wrist
• Pain primarily at the wrist, may radiate to forearm, arm, or shoulder
• Sensory findings: paresthesia and sensory loss in the thumb, index and lateral half of ring fingers of affected hand
  
  • Often noted more at night
• Motor findings: Weakness of thumb abduction and atrophy of the thenar eminence
• Diagnostic signs:
  
  • Phalen’s Sign: elicited when wrist flexion produces paresthesias in the median nerve distribution
  • Tinel’s Sign: present when tapping over the median nerve at the wrist elicits paresthesias in the median nerve distribution
• NCS: focal slowing or conduction block of median nerve fibers
• Treatment: wrist splints in mild cases and surgical decompression in severe cases

Question 23

Ulnar Nerve

Answer 23

Responsible for:

• Wrist flexion
• Flexion of 4^th and 5^th digits
• Thumb adduction
• Finger abduction and adduction

Question 24

Ulnar Neuropathy

(Cubital Tunnel Syndrome)

Answer 24

Nerve entrapment due to compression of the ulnar nerve in the cubital tunnel at the elbow.

• Sensory signs: numbness of the little finger and half of the ring finger
• Motor signs: decreased grip and problems with finger dexterity
• NCS: Slow conduction velocity at the elbow, or conduction block
• Treatment: avoidance of behaviors involving leaning on elbows, elbow pads or surgical decompression in severe cases

Question 25

Radial Nerve

Answer 25

Responsible for: * Supination of forearm * Brachioradialis reflex * Extension of fingers, thumb, wrist, and elbow

Question 26

Radial neuropathy “Saturday Night Palsy”

Answer 26

Results from **compression of the radial nerve** at the _radial/spiral groove._ * Classic case seen with sleeping with arm draped over a chair * Can also be seen with **humerus fracture** or other insult * _Sensory sx:_ **sensory loss over lateral dorsal hand** * _Motor sx:_ **wrist drop, finger drop, weakness of supination, mild elbow flexion weakness** * Treatment is **supportive** with generally spontaneous recovery

Question 27

Peroneal (Fibular) Nerve

Answer 27

* **Deep peroneal nerve** * Ankle and toe dorsiflexion * Foot eversion * **Superficial peroneal nerve** * Sensory over anterior and lateral lower leg

Question 28

Peroneal Neuropathy

Answer 28

Results from **compression of the peroneal nerve** as it _wraps around the fibular head._ * Often results from **leg crossing, prolonged bedrest, knees casts, fibular fractures** * Motor sx: **weakness of toe and foot dorsiflexion and foot eversion** * Sensory sx: **sensory loss over the dorsum of the foot and lateral distal lower extremity** * NCS: Slow conduction velocity at fibular head * Management is usually supportive with removing cause of compression

Question 29

Lateral Femoral Cutaneous Nerve

Answer 29

Provides _sensation_ to the: * Anterior thigh * Knee * Upper part of lateral thigh

Question 30

Lateral Femoral Cutaneous Neuropathy | (Meralgia Paresthetica)

Answer 30

Results from **entrapment of the lateral femoral cutaneous nerve** as it _passes under the inguinal ligament._ * Causes include **tight clothing, obesity, and pregnancy** * Presents with **paresthesias in the lateral thigh** * NCS/EMG not helpful * Tx: supportive, meds

Question 31

Mononeuritis Multiplex

Answer 31

* Less common focal neuropathy * **Painful, asymmetrical, asynchronous sensory and motor peripheral neuropathy** * Involves **isolated damage to at least two separate nerve areas** * Multiple nerves can be affected * Can be confused with polyneuropathies * As condition worsens, becomes less multifocal and more symmetrical * Has variable etiologies including **vasculitis, DM, HIV, CMV**

Question 32

Polyneuropathy Overview

Answer 32

Generalized process **affecting many peripheral nerves.** * Most common pattern of peripheral nerve disease * Usu. occurs as a side effect of medication or manifestation of systemic disease * Can be caused by both axonal degeneration and demyelinating disease * Affects longest nerves most severely * Presents first with **distal signs** in the arms and legs * Muscle weakness of the hands and feet * Loss of sensation in what is refer to as the "**glove and stocking" distribution** * Tends to be **symmetric**

Question 33

Polyneuropathy Etiologies

Answer 33

* Usu. occurs as a side effect of medication or manifestation of systemic disease * **DM, ETOH, HIV, CMT** * Peripheral nerves susceptible to various factors ⇒ ∆ health & function ⇒ polyneuropathy * **Toxins** (acrylamide and hexacarbons) * **Chemotherapeutic agents** such as Vincristine and Isoniazid * **Inflammation** (Amyloidosis) * **Dietary** * **Metabolic** (B₁₂, hypothyroid) * **Hereditary** * **Infection** (VZV, Leprosy) * **Parainfectious**

Question 34

Polyneuropathy Clinical Manifestations

Answer 34

* **Length dependent sensory loss and weakness** * **Reflexes are decreased** * **Autonomic dysfunction** can occur in severe cases * Sx may be variable

Question 35

Polyneuropathy Neurodiagnostic Testing

Answer 35

Abnormal studies provide a higher level of specificity Unclear etiology ⇒ NCS/EMG testing * **EMG w/ axonal neuropathy** * Systemic disorder, toxins, drugs * **EMG w/ demyelinating neuropathy** * Autoimmune or hereditary d/o * **EMG w/ mixed neuropathy** * Work-up same as demyelinating physiology * If not diagnostic, then evaluate for axonal causes

Question 36

Diabetic Polyneuropathy

Answer 36

* **Most common cause of neuropathy** * Most common complication of DM * Involves **peripheral and autonomic nervous system** * Has a distal-proximal gradient * **Duration and severity of hyperglycemia** ⇒ crucial risk factor for development of diabetic neuropathy * **Microvascular injury to blood vessels that supply the nerve** * Prominent axonal degeneration w/ myelin debris, distal \> proximal * _Sx vary depending on areas affected:_ * Sensitive to touch * Pain * Anesthesia * Burning sensation * Muscle weakness or wasting * Ataxia * Treatment includes **better glycemic control, gabapentin, pregabalin, SSNRI**

Question 37

Vitamin B₁₂ Deficiency Neuropathy

Answer 37

* Vit B₁₂ is an **essential nutrient** * **Deficiency is common in the US** * 10-25% of people \> 80 y/o may have Vit B₁₂ deficiency * _Multiple etiologies:_ * Strict vegetarian diet * Inability of stomach acid to aid in absorption * Pernicious anemia * Ass. w/ i**mpaired erythropoiesis** and **nervous system demyelination** * Early dx is important * Treatment: ↑ Vit B₁₂ in diet, oral or subcutaneous supplements if needed

Question 38

Alcoholic Neuropathy

Answer 38

* ETOH abuse ⇒ high incidence of polyneuropathy * **Primarily an axonal neuropathy** * Complicated by **demyelination** when associated w/ **nutritional deficiency** * Predominant ↓in density of **small myelinated and unmyelinated fibers** * **Gradually progressive** * Clinically sx usually **symmetric and predominantly distal** * Sx include **numbness, paresthesias, burning pain, weakness, cramps and ataxia** * Specific treatment is not available * Pts should receive **thiamine** * Improved nutrition and cessation of drinking have been associated with sx improvement

Question 39

Guillain-Barre Syndrome (GBS) ("Acute Inflammatory Demyelinating Polyneuropathy (AIDP)"

Answer 39

**Severe** **ascending, symmetric weakness** with **areflexia.** * Rapidly progressive **acute segmental demyelination** * **± P****receding illness** * Distal to proximal gradient * Begins with **distal paresthesias**, **pain in back/neck**, and **leg weakness** * ± Cranial nerve involvement * ± Secondary respiratory failure * ± Autonomic instability ⇒ arrythmia and BP changes * Progresses for up to **several weeks** * ↑ CSF protein but normal WBC count (albumnio-cytological dissociation) * NCS/EMG: slow conduction velocities or conduction block * Management: **Plasmapheresis** or **IVIG** ⇒ slows progression

Question 40

Chronic Inflammatory Demyelinating Polyneuropathy

Answer 40

* _Immune mediated_ attack of **peripheral myelin** * **Slowly progressive**, **usually symmetric weakness and sensory loss** _over months to years_ * **Sensory loss to all modalities**, usually worse in BLE * **Generalized hyporeflexia** * ± Nerves enlargement * ↑ CSF protein * NCS/EMG: prolonged distal latencies, significantly slowed conduction velocities, conduction block * Treatment includes steroids, plasmapheresis, IVIG, and immunosuppressants

Question 41

Demyelinating Neuropathies Other Etiologies

Answer 41

* Infectious mononucleosis (occasionally) * Toxic polyneuropathies * tri-(ortho) cresyl phosphate * [Ginger Jake (leg) Paralysis] * Reactions to immunization: Vaccination for the swine flu scare [1976]

Question 42

Varicella-Zoster Virus

Answer 42

* **Infectious Polyneuropathy** * One of the most common viral infections of the PNS * **Latent infection of neurons in the sensory ganglia** of the spinal cord and brain stem follows **chickenpox** * **Reactivation** ⇒ painful, vesicular skin eruptions in the _distribution of sensory dermatomes_ (***shingles***) * Most frequently thoracic or trigeminal * Virus may be transported along the sensory nerves to the skin ⇒ **active infection of epidermal cells** * _Affected ganglia_ ⇒ **neuronal destruction**, **mononuclear infiltrates** * _Peripheral nerve_ ⇒ **axonal degeneration** after the **death of the sensory neurons**

Question 43

Leprosy

Answer 43

* **Infectious polyneuropathy caused by** *Mycobacterium leprae* * _Lepromatous leprosy:_ * **Schwann cells** **invaded** by *M. leprae* → proliferates and infects other cells * **Segmental demyelination and remyelination** * _Tuberculoid leprosy:_ * CMI response to *M. leprae* → **granulomatous inflammation** in the dermis * Injures nearby cutaneous nerves → **localized nerve involvement**

Question 44

Hereditary Neuropathies

Answer 44

Heterogeneous, usu. progressive, and often disabling syndromes that affect peripheral nerves.

Question 45

Hereditary motor and sensory neuropathies (HMSN)

Answer 45

* Most common form of hereditary neuropathies * **Charcot-Marie-Tooth** disease and **Dejerine-Sottas** disease * Caused by mutations in genes involved in the **formation and maintenance of myelin**

Question 46

Charcot Marie Tooth (CMT)

Answer 46

**Hereditary motor and sensory neuropathy** * _Clinical manifestations:_ * **Foot drop** * **Claw toe / hammer toes** * **Pes cavus** (high arch of foot) * Wasting of hands, feet, and distal leg muscles * Mild sensory loss * Enlarged nerves * Pathology: **demyelination and onion bulbs** * Multiple variants with different transmission patterns: **autosomal dominant, autosomal recessive, or X-linked**

Question 47

Hereditary Sensory and Autonomic Neuropathies (HSAN)

Answer 47

Numbness, pain, and **autonomic dysfunction** → orthostatic hypotension

Question 48

Familial Amyloid Polyneuropathies | (FAP)

Answer 48

* **Deposition of amyloid** within the PNS * Most types exhibit mutations of the ***transthyretin* gene** * Clinical presentation is similar to that of HSAN * Numbness, pain, and autonomic dysfunction

Question 49

Traumatic Neuropathies

Answer 49

* Peripheral nerves commonly injured in the course of trauma * Lesions include **lacerations and avulsions** * **Re-growth** may be complicated by **discontinuity b/t proximal and distal portions of the nerve sheath** as well as by the **misalignment of individual fascicles** * Dysregulated/abnormal axonal growth ⇒ mass of tangled axonal processes called a **traumatic neuronal** (pseudoneuroma or amputation neuroma)

Question 50

Other Etiologies of Polyneuropathy

Answer 50

* Long standing HIV * Critical Illness * Uremic polyneuropathy * Amyloidosis * Hypothyroidism * Vitamin Deficiencies * Lyme disease * Paraneoplastic * Heavy metal * Connective Tissue Disease (Sjogrens) *

Question 51

Pressure Palsy

Answer 51

Nerve dysfunction seen after pressure is applied to nerve

Question 52

Radiculopathy Overview

Answer 52

* **Due to damage to a nerve root** * **Disc herniation** is the most common cause * Characterized by **sensory complaints in a dermatomal distribution** and **weakness in the muscles innervated by the root** * If nerve root involved in a reflex, **reflex may be decreased** * Pain * NCS/EMG: sensory AP’s are normal, EMG w/ fibrillations in paraspinal muscles (acute) * Treatment: * Supportive - PT, pain management * Surgery

Question 53

Cervical Radiculopathy

Answer 53

Presents with neck pain, arm pain, or both Sensory and/or motor deficits

Question 54

C6 Radiculopathy

Answer 54

* C5-C6 disc herniation * Weakness of **shoulder abduction, elbow flexion, wrist flexion/extension** * Sensory loss of the **lateral forearm, thumb, and index finger** * **Loss of bicep and brachioradialis reflex**

Question 55

C7 Radiculopathy

Answer 55

* C6-C7 disc herniation * **Most common cervical radiculopathy** * Weakness of **elbow and wrist extension** * Sensory disturbance of **middle finger** * Pain in neck and dorsum of forearm * **Loss of triceps reflex**

Question 56

Lumbosacral Radiculopathy

Answer 56

* Pain syndrome caused by **compression or irritation of nerve roots in the lower back** * Caused by **lumbar or sacral disc herniation, DDD, and narrowing of foramen** where nerve exits * Results in **low back pain with radiation to the leg**

Question 57

L2,3,4 Radiculopathy

Answer 57

* Marked overlap of L2, L3, L4 innervation * Radiculopathies considered as a group * Most commonly involved in _older pts_ with sx of **spinal stenosis** * **Acute back pain** **→** **anterior thigh** **→** **knee** **→** **medial lower leg** **→** **arch of the foot** * Weakness: **hip flexion, knee extension, hip adduction** * ↓ Sensation: **anterior thigh to medial lower leg**

Question 58

L5 Radiculopathy

Answer 58

* **Most common radiculopathy affecting the lumbosacral spine** * **Back pain** **→** **lateral aspect of the leg** **→** **dorsum foot** * ↓ Strength in **foot dorsiflexion, toe extension, and foot eversion** * ± Weakness of **leg abduction** in severe cases * **Atrophy of the extensor digitorum brevis** of muscle of the foot and **tibialis anterior** of the lower leg * Reflexes are normal

Question 59

S1 Radiculopathy

Answer 59

* **Pain** **→** **posterior aspect of the leg** **→** **foot from the back** * Weakness of **plantar flexion** * ± Weakness of **leg extension and knee flexion** * Sensation is reduced on the **posterior aspect of the leg** and **lateral edge of the foot** * **Loss of ankle reflex**

Question 60

Plexopathy

Answer 60

* Disorder affecting a **network of nerves, blood vessels, or lymph vessels** * **Brachial or lumbosacral plexus** * Sx include pain, loss of motor control, atrophy and sensory deficits * The entire plexus, or just portions may be involved

Question 61

Brachial Plexopathy

Answer 61

* Can be d/t compression, transection, ischemia, inflammation, metabolic abnormalities, neoplasia, radiation therapy, trauma, burns, postoperatively, autoimmune or post-infectious, or direct infiltration * **Muscle weakness, atrophy, sensory loss, and pain** * _Acute onset_ ⇒ pain in the shoulder and upper arm * _Insidious onset_ ⇒ progressive pain, evolving numbness, weakness of selected muscle groups

Question 62

Lumbosacral Plexopathy Clinical Manifestations

Answer 62

Pattern of weakness/numbness helps localize lesion: * _Lumbar plexus:_ * Weakness of **hip flexion and adduction** and/or **knee extension** * Sensory disturbance in **anterior thigh and medial leg** * _Lumbosacral trunk and upper sacral plexus:_ * **Foot drop, flail foot, weakness of knee flexion or hip abduction** * Sensory disturbance in **leg, dorsum of foot, posterior thigh, perineum**

Question 63

Lumbosacral Plexopathy

Answer 63

* Secondary to various causes including: DM, neoplasms, ischemia, post-op, trauma, surgery (OB), infection, CT disorder * Often results from **mass lesions** * Compression from pelvic tumors * Psoas abscess * Retroperitoneal hemorrhage * **Asymmetric, focal weakness, numbness, dysesthesia and/or paresthesia** in _multiple lumbosacral nerve root distributions_ * Pattern of weakness/numbness helps localize lesion * _Lumbar plexus:_ * Weakness of **hip flexion and adduction** and/or **knee extension** * Sensory disturbance in **anterior thigh and medial leg** * _Lumbosacral trunk and upper sacral plexus:_ * **Foot drop, flail foot, weakness of knee flexion or hip abduction** * Sensory disturbance in **leg, dorsum of foot, posterior thigh, perineum**

Question 64

Motor Neuron Disease

Answer 64

_Neurodegenerative disorders_ that selectively affect **motor neurons of the spinal cord** * ALS is most common * Can have UMN + LMN signs or just LMN * Progressive

Question 65

Amyotrophic Lateral Sclerosis | (ALS)

Answer 65

Neurodegenerative disease of the **upper and lower motor neurons.** * **Onset 55-75 years** * _UMN dysfunction_ ⇒ **increased tone, spasticity, hyperreflexia and positive Babinski** * _LMN dysfunction_ ⇒ **atrophy, weakness, fasciculation and loss of reflexes** * Extraocular muscles and sensation usually spared * Late in course, **spasticity** may occur * _Bulbar weakness_ ⇒ **dysarthria, dysphagia** * Pts present with **asymmetric distal weakness** * Usually weakness starts in one region then spreads to adjacent regions then spreads to contralateral limb * Pts often die with **respiratory insufficiency or aspiration pneumonia** * Management: **Supportive** (multidisciplinary clinics), **Riluzole** (may prolong survival)