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Flashcards in Motor Neuron Diseases Deck (45):
1

What is affected in Motor Neuron Diseases

-motor neurons, their motor axons, and secondarily the muscle fibers they innervated (the motor unit)

2

Werdnig-Hoffman

Infantile Spinal Muscular Atrophy
-autosomal recessive
-hypotonicity, hyporeflexia, fatal
-tongue fasciculations
-poor suck reflex
-abdominal respirations
Anterior Horn Cell Disease
-difficulty breathing, swallowing , die early from respiratory failure, "frog-leg" posture

3

Wolfart-Kugelberg-Welander

-Juvenile Proximal Chronic Spinal Muscular Atrophy
-Autosomal recessive
-slowly progressive, fasciculations, proximal weakness, resembles myopathy
Anterior Horn Cell Disease
-atrophy of pectoralis & thigh muscles

4

Adult Onset Spinal Muscular Atrophy

-sproadic (some familial)
-Proximal, distal weakness
-hypotonicity, hyporeflexia
Anterior Horn Cell Disease

5

Werdnig-Hoffman Disease Tests

-EMG: signs of denervation and fasciculations
-Muscle Biopsy: group fiber atrophy
-Mutation: 'survival motor neuron gene' on chromosome 5q

6

Wolfart-Kugelberg-Welander Tests

-EMG & Biopsy: denervation changes
-Serum CK: normal
-Mutation: 'survival motor neuron gene' SNM1 is absent and the size of SMN2 determines if the patients have neonatal or juvenile form
-SMN2 is larger

7

Progressive Bulbar Palsy

Adult motor neuron disorders
-sproadic, fasciculations, Bulbar muscles weakness, rapidly progressive, tongue atrophy
-may develop ALS

8

Amyotrophic Lateral Sclerosis (ALS)

Adult motor neuron disorders
-mostly sporadic, some familial cases - 10%, hyperreflexia, spasticity
-muscle atrophy (fasciculations) , fasciculations, tongue atrophy, rapidly progressive (lethal)
-upper & lower motor neurons, bulbar weakness
-normal sensation

Presentation: difficulty swallowing & breathing
Late: biateral Babinski signs, hard to close mouth

9

Progressive Lateral Sclerosis

-sporadic, involves only upper motor neurons, spasticity
-hyperreflexia, more benign course
-little atrophy or signs of denervation

10

Progressive Spinal Muscular Atrophy

-mostly sporadic, progressive weakness, muscle atrophy, fasciculations, areflexia

11

Signs, Symptoms, & Labs of Motor Neuron Diseases

-Symmetrical or asymmetrical weakness
-Atrophy
-inc. or dec. reflexes dep. on corticospinal tract involvement (ALS)
-fasciculations
-normal sensation
-normal nerve conduction velocities
-denervation on EMG
-dec. # of motor units
-muscle biopsy shows atrophic fibers & fiber grouping

12

Cervical Spondylosis

-seen in MRI
-present: lower motor neuron signs in upper extremities secondary to nerve root compression & upper motor neuron signs in the lower extremities secondary to compression of spinal cord & corticospinal tracts

13

Kennedy's Disease

-Bulbo-spinal muscular atrophy
-more benign than ALS, family history
-mutations of the androgen receptor on the x chromosome
-Phenotype: gyneocomastia & testicular atrophy, lower motor neuron syndrome (atrophy, fasciculations, signs of denervation in limbs & tongue, mild neuropathy)
-serum CPK elevated
-DNA testing diagnostic

14

Pathology of ALS

-degeneration of the corticospinal tracts (lack of myelin)
-Bunina body: dense granules inclusion in cell body cytoplasm (ubiquitin accumulations)

15

Etiology of ALS

-unknown, some familial cases (genetic)

16

Possible etiologies of ALS and other motor neuron diseases

Genetic Defects
-SOD gene mutations in chromosome 21 in AD familial ALS
-Juvenile ALS: chromosome 2q33 (also 9q34, 15q15, 8q21), and also ALS associated with mutation of 9q21, XP
-ALS associated with other diseases such as chromosome 17-linked fronto-temporal dementia (FTD)
-an expanded section of DNA on chromosome 9 in the gene C90RF72 is most common cause of familial ALS with or without FTD
-Excitotoxicity: evidence suggests an inc. of glutamate mediated excitotoxicity causing neuronal degeneration (secondary)

17

Treatment of ALS

-Glutamate antagonists (riluzole)
-Experimental: creatine & antioxidants such as carotene, coenzyme Q10, vitamins C & E could be of benefit, COX 2 inhibitors, nerve growth factors
-physical therapy
-symptomatic treatments such as anticholinergics for sialorrhea, stool softeners, antispastic drugs, botulinum toxin
-antidepressantts
-bracing
-gastrostomy
-respiratory assistance

18

Brachial plexus

-extends from spinal cord to distal aspect of axilla
-6 divisions, behind clavicle

19

Sensory Domain

-the skin region innervated by the sensory nerve fibers contained with a nerve root
-Dermatome: sensory domain of a root

20

Muscle Domain

-the muscles innervated by the motor nerve fibers contained within a nerve root
-Myotome: motor domain of a root

21

What are the 2 most common causes of radiculopathies?

1. Disk herniation & degeneration (>C6
-Spondylosis: C5 & C6> frequent
by age 60 yrs, 70% W and 85% M
after age 70 yrs, 93% W and 97% M

2. Lumbosacral radiculopathies
->95% of HNPs affect either L5 or S1

22

Clinical features of Radiculopathies?

-Pain (hallmark): sharp, stabbing, hot; electric, radiating, aggravated by maneuvers that stretch the root (cervical: neck extension, neck rotation, Spurling's maneuver)
-lower extremity (SLR used with L5 or S1 nerve root involvement is suspected and reverse SLR w/L4

-weakness & atrophy (motor nerve fibers, myotomal distrubution (muscle domain of root))
-Paresthesias & sensory loss: sensory nerve fibers, dermatomal distribution (sensory domain of a root)
-Muscle stretch reflexes (diminished or absent)

-Irritation = tingling

23

Spondylosis

>50 yrs
-Cervical spondylosis: myeloradiculopathy (spinal canal stenosis)
-Lumbosacral spondylosis: neurogenic cladication (ambulation to LE pain & weakness), cauda equina syndrome

24

Radiculopathy: Fracture of Dislocation

-Trauma: major cause in young patients
minor cause amoung elderly
-Bone disease: osteoporosis; osteomalacia; Paget disease, Corticosteroid therapy, congenital anomalies

25

Radiculopathy: Infection

-fever
-immunosuppressed status
-IVDA
-Spinal surgery
-penetrating wound

26

Radiculopathy: Neoplasm

-history of cancer
-constitutional symptoms (weight loss)
-pain at rest
-neurologic deficit (cauda equina localization)

27

Evaluation of Radiculopathy

-H&P (most important):
Spinal cord compression: sensory level, anal tone, fecal or urinary incontinence, check cutaneous reflexes (abdominal; bulbocavernousus; anal wink; cremaster)
-Plain radiographs
-CT (+/- myelography)
-MRI: superior to CT for all spine conditions
multiplanar
greater contrast sensitivity (tumor & infection)
Noninvasive
Non-ionizing radiation
Gadolinium contrast (scar tissue vs. recurrent disk protrusion)

28

EDX Testing

-yields physiologic info
-complements MRI (anatomic changes, high false+)
-False + studies extremely uncommon

-assesses sensory & motor nerve fibers
-assesses muscle fibers
-identifies demyelination & axon loss
-localized the disorder
-generates ddx or the actual diagnosis
-determines severity
-determines prognosis
-dictates management & follow-up

29

Radiculopathy: Conservative Treatment

-most w/acute radiculopathies improve in 6 weeks
-bed rest 0-2 days
-physical therapy (heat, cold, ultrasound, massage, stretching, ergonomic education)
-Meds: NSAIDS, prednisone, benzodiazephines
-Nerve Block

30

Radiculopathy: Surgical Treatment

-Etiology (neoplastic process)
-spinal instability
-severe or progressive weakness
-spinal cord compression
-cauda equina syndrome
-sphincter or sexual dysfunction
-incapacitating neurogenic claudication
-intractable pain (ill-advised if isolated pain with negative imaging)

31

Plexopathies

-Brachial plexus elements
(anterior primary rami, trunks, divisions, cords, terminal nerves)

32

Polyneuropathy

-weakness symmetrically, distally
-stocking & glove pattern
-dec. reflexes
-slow nerve conduction velocities
-denervation & decreased # of motor units on EMG
-Muscle biopsy: atrophic fibers & fiber type grouping

33

Mononeuritis

(one nerve)
-weakness in nerve distribution
-slow nerve conduction velocities
-denervation & decreased # of motor units on EMG
-Muscle biopsy: atrophic fibers & fiber type grouping

34

Mononeuritis Multiplex

-several nerves
weakness in nerve distribution
-slow nerve conduction velocities
-denervation & decreased # of motor units on EMG
-Muscle biopsy: atrophic fibers & fiber type grouping

35

Demyelinating Neuropathy

-weakness: distal & proximal
-areflexia
-dec. vibration & position sense with little deficit of pain & temp sensations
-very slow NCV, conduction block with normal amplitude of nerve action potential
-prolonged distal latencies, F responses & H reflexes

36

Axonal Neuropathy

-mostly distal weakness with distal areflexia, glove & stocking sensory deficit to all modalities, trophic changes
-Nerve conduction is almost normal with reduced action potential amplitude, signs of denervation on EMG (uremia, toxins)

37

Wallerian Degeneration

-severe acute damaged to myelin & axons
(trauma, vasculities)

38

Charcot-Marie-Tooth Disease

-hereditary
-usually autosomal dominant
-usually demyelinating, rarely axonal
-high arched feet
-hammer toes
-check NCV in relatives
-some cases appear late
-Type 1 has deletions on the genes that express meylin protein PMP 22(1A) or protein 0 P0(1B)

39

Diabetic Neuropathies

-diffuse sensory motor neuropathy has metabolic origin (accumulation of sorbitol, deficiency of myoinositol)
-presens with burning of feet, then numbness & weakness
-improves with good control of diabetes
-mononeuritis, mononeuritis mulitplex & diabetic ophthalmoplegia are produced by infarct to nerves or plexus
-diabetics are more predisposed to entrapment neuropathies

40

Treatment of Diabetic Polyneuropathy

-good control of diabetes
-nerve growth factor
-sorbitol antagonist
-myoinositol & vitamin supplementation
-be aware of other conditions (CIDP)

41

Treatment of Mononeuropathy, mononeuropathy multiplex

-treatment is conservative, consider steroids if the disease is progressive

42

Guillain-Barre syndrome

-acute autoimmune, ascending paralysis accompanied by arreflexia & normal or mildly abnormal sensation with albuminocytological disassociation in the spinal fluid

43

Guillain-Barre syndrome: Clinical Findings

-progressive (symmetrical) paralysis over a period of one to three weeks
-acute inflammatory radiculoneuropathy
-ascending paralysis, facial weakness, respiratory insufficiency
-paresthesia but little evidence of sensory deficit
-areflexia, normal or almost normal sensation

44

Treatment of Guillian Barre Syndrome

-respiratory assistance if necessary
-includes plasmapheresis or gamma globulin infusions
-corticosteroids (NO benefit)
-physical therapy & emotional support

45

Chronic Inflammatory Neuropathy

-autoimmune inflammatory neuropathy that affects myelin sheath
-subacute to chronic weakness; symmetrical, distal & proximal
-no cranial nerve involvement
-areflexia
-marked deficit of positional & vibratory senses, little pain & temp deficit, elevated spinal fluid protein, slow NCV
-evidence of conduction block (vasculitic neuropathy sometimes produces conduction block, simulating demyelination)
-minimal denervation on EMG
-rarely can have CNS signs (central demyelination)
-could have relapsing course
-nerve biopsy: segmental demyelination, rarely, inflammation
-same patients have MUGS
-treat with corticosteroids, immunosuppressant, or gamma globulin