Disorders of Anterior Horn/Peripheral Nerves & NMJ Flashcards
Signs/symptoms of upper motor neuron disorders
- spastic tone
- hyperactive tendon reflexes
- pathologic reflexes (Babinski)
- emotional lability (inappropriate laughing and crying)
Signs/symptoms of lower motor neuron disorders
- muscle atrophy
- fasciculation
- diminished tone (flaccidity)
- reduced or absent reflexes
Signs/symptoms of non-motor (sensory or autonomic) peripheral nerve disorders
- sensory
- numbness
- pain
- altered sensation
- autonomic
- bowel, bladder disturbance
- altered sweating, HR, BP
Conditions w/rapidly developing muscle weakness
- NMJ disorders
- myasthenia gravis
- botulism
- organophosphate poisoning
- acute demyelination
- Guillain Barre
- electrolyte disturbance
- toxic myopathies
Electrodiagnostic studies in peripheral nerve disorders
- nerve conduction studies
- demyelinating ==> slow NCS
- vs. axonal neuropathy ==> decreased amplitude NCS
- needle electromyography (EMG)
- neuropathic (anterior horn/peripheral nerve) ==> loss of whole motor unit
- vs. myopathic ==> drop out of biers w/in motor unit
Anterior Horn cell disorders (examples)
Amyotrophic lateral sclerosis*
Spinal muscular atrophy
Poliomyelitis and West Nile virus
Radiculopathies & plexopathies examples
Cervical (neck) and lumbosacral (back) nerve root compression (common)
Brachial and lumbosacral plexopathies
Peripheral neuropathies (mononeuropathy examples)
Carpal tunnel syndrome - entrapment of median nerve at wrist
Ulnar nerve palsy –entrapment at elbow
Peroneal palsy – entrapment at the head of the fibula
Peripheral neuropathies (polyneuropathy examples)
Hereditary – Charcot Marie Tooth disease*
Systemic disease – diabetes*, immune disorders etc
Vitamin deficiency – B12 deficiency, etc.
Exogenous toxins – alcohol, chemotherapy, etc.
NMJ disorders
Myasthenia gravis*
Botulism
Organophosphate poisoning
Myopathies examples
Muscular dystrophies – Duchenne/Becker*
Myotonic disorders
Inflammatory myopathies – polymyosits, dermatomyositis
Metabolic myopathies – glycogen storage, lipid myopathy
Endocrine/toxic myopathies
ALS signs/symptoms
- progressive weakness & wasting
- coexisting: spasticity & hyperreflexia
- asymmetric limb weakness + fasciculations
- foot drop or hand deformity possible
- speech may be slurred/spastic
- diaphragm weakness ==> decreased breathing capacity + impaired swalling ==> aspiration pneumo or respiratory insufficiency
ALS pathology
- anterior horn cell disorder
- brainstem + lower motor neuron degeneration ==> weakness/wasting
- UMN degeneration ==> hyperreflexia/spasticity
*
Sx management of difficulty speaking, swallowing, breathing
- alternative communication devices
- feeding tube
- positive pressure ventilation
- mask
- tracheostomy
Charcot Marie Tooth Disease types
- CMT Type 1:
- slow nerve conduction velocities
- pathological evidence of hypertrophic demyelinating neuropathy
- CMT Type 2:
- normal nerve conduction velocity
- axonal degeneration
CMT genetic inheritance patterns
- Autosomal dominant ==> CMT Type I & II
- CMT1A = duplication of PMP22 (most common)
- PMP22 = peripheral myelin protein gene
- Autosomal recessive, X-linked ==> CMT type IV
CMT presentation (signs/symptoms)
- phenotype A:
- child begins to walk normally
- distal (hands/feet) weakness & sensory loss develops during first two decades of life
- ==> walks w/brances
- phenotype B:
- impaired as infants ==> delayed walking
- ==> wheelchair-bound
- phenotype C:
- adult-onset
Most common type of diabetic neuropathy + presentation
- distal sensory or sensorimotor polyneuropathy
- initial numbness and burning dysesthesias in feet ==> legs & hands
- weakness of foot dorsiflexor ==> foot drop gait
- diminished grip strength/hand dexterity
Sensation in diabetic neuropathy
- loss of pin sensation in stocking glove distribution (often asymmetric)
- “Large fiber pattern”
- loss of position, vibration and light touch
- decreased reflexes
- “Small fiber injury”
- prounounced loss of pain and temperature sensation
- w/pain (dull aching; distal burning @ night)
- NCVs may be near normal
- autonomic dysfunction
Other possible neuropothies w/diabetes mellitus
- Lumbosacral plexopathy signs/symptoms
- acute onset of asymmetrical proximal weakness and pain of legs
- frequently @ onset of diabetes w/weight loss
- mononeuropathies @ peripheral nerves
Pathogenesis of diabetic neuropathies
- varied
- metabolic derangements ==> vascular changes ==> ischemic ==> neuropathies
Myasthenia Gravis presentation (signs/symptoms)
- fluctuating weakness & fatigue @ cranial, limb, or trunk musculature
- ocular sx: ptosis, diplopia and blurred vision
- weak facial muscles ==> slurred/nasal/hoarse speech
- ==> trouble chewing/swallowing
- weak respiratory muscles ==> SOB
Pathogenesis/tx of MG
- autoimmune disorder
- Ab against post-jxnal AChR
- Tx
- oral cholinesterase inhibitors (symptomatic relief, temporary)
- corticosteroids + immunosuppresion
- plasma exchange
- thymectomy
Duchenne/Becker MD presentation (signs/symptoms)
- Duchenne
- clumsy, waddling gait
- lumbar lordosis ==> protuberant abdomen
- pseudohypertrophy of calves
- toe waling
- Gower’s maneuver
- mental impairement common
- Becker
- later onset
- more benign course
- longer survival
Duchenne/Becker MD genetic components
- X-linked recessive
- deletions, duplication, point mutations @ gene on X chromosome for dystrophin membrane protein
- common mutations:
- reading fraime shift ==> premature stop
Labs associated w/DMD/BMD
- highly elevated serum CK
- biopsy/EMG show myopathic features
- genetic testing
Sx management in DMD/BMD
- PT/OT
- stretching ==> prevent contractures
- respiratory therapists ==> BiPAP, assistive cough, chest percussion
- ==> full-time ventilation
