Neuropathy, Myopathy, and Motor Neuron Disease Flashcards
mononeuropathy
involvement of a single major named nerve usually by trauma or compression (median n at wrist, ulnar n at elbow, common peroneal n at fibular head)
polyneuropathy (peripheral neuropathy)
d/o of multiple major and small nerves or branches
what happens in the most common polyneuropathies
s/s are symmetrical and sensory loss or impairment occurs early and often remains prominent
where does numbness and tingling usually befin
distally in the toes and feet, later affecting the fingers and hands
what happens if autonomic nerves are involved
- orthostatic hypotension
- incontinence
- impotence
- sweating abnormalities
what are the basic pathological processes in neuropathy?
demyelination and axonal degeneration
demyelination
- characterizes a mononeuropathy from focal compression such as carpal tunnel syndrome where median n is compressed at the wrist
- also primary process of G-Barre (acute polyneuropathy)
role of axonal degeneration
-if neuropathy progresses over time or is initially several axonal degen may also occur with less chance for recovery
Wallerian degeneration
when there is a more severe crush or penetrating focal nerve injury, axonal loss occurs via wally
-axons and myelin degenerate distal to the point of nerve injury
polyneuropathies from toximetabolic causes
mostly have axonal degeneration as the primary pathology
multiple mononeuropathy
can be d/t systemic illness which is inflamm/ai (SLE), infiltrative (sarcoidosis), or infectious (leprosy)
causes of polyneuropathy
- meds (chemo)
- neurotoxins
- alcoholism
- malnutrition and vitamin deficiencies
role of EMG in diagnosis
-tests the electrical activity and function of nerves and muscles
sural (sensory nerve) biopsy
- used when the clinical pic or EMG suggests a chronic polyneuropathy d/t an inflamm, immune-mediated, or vasculitic cause
- leaves permanent numbness along lateral foot
oral medications for neuropathic pain
- anticonvulsants (Gabapentin, Pregabalin, Carbamazepine)
- antidepressants (Duloxetine, Amitriptyline)
Guillain-Barre
- one of the most rapidly progressive polyneuropathies
- usually s/p recent viral illness
- immune system targets peripheral nerve myelin
- ascending areflexic paralysis (lower limbs affected first)
how can you hasten recovery for G-B
plasmapheresis or IVIG infusion
what is one of the most common chronic polyneuropathies (occurs over months to yrs)
DM-which may also cause:
- isolated or multiple mononeuropathies
- autonomic neuropathies (diabetic gastroparesis or orthostatic hypoTN)
- cranial neuropathies (diabetic third nerve palsy)
what are some other causes of polyneuropathies?
- metabolic or endocrine disorders
- rheumatologic disease
- cancer or myeloma
- infection
- nutritional deficiencies
- toxins
characteristics of most myopathies
-proximal weakness or fatigue, nml sensation, and late loss of reflexes after significant atrophy has occurred
CK creatine kinase
muscle enzyme often nonspecifically elevated in disease of muscle
polymyositis
inflammation of multiple muscle, may be d/t infections or drug reactions
-refers to ai dz affecting muscle
dermatomyositis
-both skin (rash involving periorbital areas and knuckles) and muscle are involved
Duchenne’s (X-linked) muscular dystrophy
deficiency of muscle dystrophin (important structural protein)
- Gower’s manuever
- calf muscles: pseudohypertrophy (fat and connective tissue)
myotonic dystrophy type 1 (AD)
- d/t excessive trinucleotide DNA repeats on c. 19; producing an abnml protein kinase in muscle fibers
- weakness affects the distal limbs, neck, face, and jaws
myotonia
- peculiar impaired relaxation of muscle after volitional contraction
- difficulty letting go of handshake or doorknob
- also: cataracts, frontal baldness, infertility, cardiac arrhythmias
UMN (CS+CB)
-UMN comprise the corticospinal tract (control anterior horn cells) and corticobulbar tract (CN motor nuclei-LMN)
BULB
-refers to lower brain stem, location of the CN motor nuclei that innervate muscles of the jaws, face, palate, pharynx, larynx, and tongue
spinal muscular atrophy
- group of disorder involving just anterior horn cells
- clinical findings: LMN signs
- Werdnig-Hoffman=example of infantile onset
primary lateral sclerosis
- familial degeneration of corticospinal tract in lateral columns of the spinal cord not due to structural (spinal stenosis from degenerative arthritis) or metabolic (vit b12 deficiency) lesions
- weakness + UMN signs
pseudobulbar palsy
-encompasses several d/o where only the corticobulbar tract is involved, causing facial wealness, impaired chewing dysarthria, dysphagia and hoarseness
what is the most common motor neuron dz
ALS
motor neuron dz diagnosis
should be made over a long period of time
ALS epi
-40-70 yo , M>W
ALS early s/s
- may start with focal weakness and atrophy in a limb such as a shoulder or leg (foot drop)
- spreads and becomes bilateral
ALS later
- both UMN and LMN degenerate + widespread fasciculations
- extraocular muscles and sphincters of bladder and bowel are spared
- rarely familial–SOD enzyme defective; more commonly sporadic
ALS pathological findings
- degeneration of corticospinal and corticobulbar tracts
- gliosis and loss of anterior horn cells and puramidal neurons
- neurogenic atrophy of muscle
ALS mimics
- cervical radiculomyelopathy (LMN in UE, UMN in LE)
- stroke
- rare ai neuromuscular disorders
ALS drugs
-Riluzole-opposes excitotoxic effect of glutamate at the NMDA receptors of motor neurons
most common site of ulnar nerve entrapment
elbow where the ulnar nerve lies at the medial epicondylar groove
ulnar nerve syndrome
-dec sensation over 4th and 5th fingers and weak grip d/t involvement of interosseous muscles of the hand
