Peripheral Nerve Disease Flashcards
What is segmental demyelination?
Damage to the myelin or Schwann cell disease
What is the process of recovery after demyelination?
- Disintegrating myelin is engulfed by Schwann cells, then by macrophages
- Axon stimulates endoneurium for remyelination
- New myelinated internodes are shorter and thinner
What are onion bulbs?
Concentric lays of Schwann cell cytoplasm and BM from sequential demyelination
Will eventually cause axonal injury
What is Guillan-barre?
Inflammation and demyelination of the peripheral nerves and spinal nerve roots
What are the sx of Guillan-Barre?
Decreased DTRs
Ascending paralysis
Increase CSF protein
What is the histo of Guillan-Barre?
Inflammation of nerves
Macrophage processes penetrate the BM of Schwann cells
Segmental demyelination
What is Guillan-Barre preceded by?
An acute flulike illness
Pathogens associated: campylobacter, CMV, EBV, mycoplasma
Mediated by T cells
What is seen in chronic inflammatory demyelinating polyradiculoneuropathy?
Symmetric sensorimotor polyneuropathy
Onion bulbs
Tx : steroids, plasmapheresis
What is seen in lepromatous infectious peripheral nerve disease?
M. Leprae invades the Schwann cells causing demyelination
Endoneurium fibrosis
Thickening of peri neural sheaths
Symmetric polyneuropathy — ulcers, wounds
Granulomatous inflammation of the dermis
What is seen in diphtheria?
Paresthesias
Weakness
Loss of proprioception and vibratory sense
Demyelination of axons in the anterior and posterior roots
What is Walllerian degeneration?
Degeneration of distal ends of fibers on a focally damaged axon
What is denervation atrophy?
When muscle fibers lose neural input
Will see angulated cells and target fibers (rounded zone of reorganization)
What is the cause of axonal degeneration and muscle fib atrophy?
Trauma
Ischemia
What happens in reinnervation?
Neighboring unaffected motor unit sprouts over to innovate the damaged segment— loss of checkerboard, get type grouping
What is the inheritance pattern of muscular dystrophy?
X linked
What is the mutation in muscular dystrophy?
Frameshift or point mutation in X that codes for dystrophin
What is dystrophin?
Cytoplasmic protein of z band that forms the interface between intracellular contractile apparatus and extra cellular connective tissue matrix
What is the histo of muscular dystrophy?
Variation in fiber size,
Muscle replaces by fat and CT
Hyper contracted fibers
What are hyper contracted fibers?
Enlarged, rounded, hyaline fiber with no cross striation in DMD
What do females who are carriers of DMD often have?
Dilated cardiomyopathy
What are the sx of DMD?
Delay in walking
Pseudo hypertrophy of calf muscles - increase in fat and CT tissue
Cardiac arrhythmias
Cognitive impairment
What are the causes of death in DMD?
Respiratory insufficiency
Cardiac decomp
Pulmonary infection
What is dystrophy is autosomal dominant in inheritance and autosomal recessive?
Limb girdle
What is the mutation in limb girdle dystrophy?
In sacroglycan complex which interacts with dystrophin via b-dystroglophin
What is the inheritance pattern of myotonic dystrophy?
Auto Dom
What is the mutation in myotonic dystrophy?
CTG repeat on ch.19 that affects DMPK
What dystrophy has ring fibers, change in intrafusal fibers, sarcoplasmic mass
Myotonic
What are the sx of myotonic dystrophy?
Abnormal gait Ptosis Cataracts Frontal balding Gonadal atrophy Dementia Decrease IgG Sustained involuntary contraction
What myopathy is due to vigorous exercise, cold, or high carb meals?
Ion channel myopathies
Which gene is mutated in the hypokalemic kind?
Gene for voltage gated calcium channel
What gene is mutated in the hyperkalemic ion channel myopathy?
Sodium channel in skeletal muscle
What is malignant hyperprexia?
Hyper metabolic state induced by halogenated anesthesias
What is abnormal in the lipid myopathies?
Carnitine transport system
Deficiency of mitochondrial dehydrogenase enzyme
What do you see in lipid myopathies?
Accumulation of lipid droplets within muscle
Myo fibrils separated by vacuoles that stain with oils red O or Sudan black
Occurs in type 1 fibers
What is seen in mitochondrial myopathies?
Aggregate of abnormal mitochondria
Ragged red fibers
Para crystalline parking lot inclusions
How do people with mitochondrial myopathies present?
With proximal muscle weakness
External ophthalmoplegia
What is dermatomyositis?
Inflammatory myopathy where there is antibody attack on the microvasculature so there is foci of ischemic myocyte necrosis
What is the morphology of dermatomyositis?
Inflammatory infiltrates around small blood vessels and in perimysium
Perifascicular atrophy
Necrotic muscle fibers and regeneration
What are the sx of dermatomyositis?
Iliac or heliotrope rash of upper eyelids with peri orbital edema
Groton lesions= scaling erythmatous eruption or dusky red patches over knuckles, elbows, knees
What disease has antibodies directed against tRNA synthetase?
Polymyositis
What disease is ANA positive, mediated by CD8 T cells and macrophages with infiltrates in the endomysium?
Polymyositis
What disease involves the distal muscles, has asymmetric weakness, amyloid deposition and is not improved by immunosuppressive therapy?
Inclusion inflammatory myopathy
What is the auto dom mutation in inclusion?
Mutation in gene for myosin heavy chain IIa
What is the auto recessive mutation for inclusion?
Mut in GNE gene
What is seen in inclusion?
Rimmed vacuoles
Amyloid deposition
Hyperphosphorylated tau protein
What disease present with proximal muscle weakness, exophthalmic ophthalmoplegia, cramping muscles, slowed reflexes, and episodic weakness with hypokalemic?
Thyrotoxic myopathy
What presents with acute pain of a single muscle group and myoglobinuria?
Ethanol myopathy
Which fibers are affected in steroid myopathy?
Type 2
What myopathy is associated with presence of vacuoles in the myocytes, autophagic membrane, curvilinear bodies?
Chloroquine myopathy
What myopathy is associated with dilation of the SR and thickening of the basal laminate and atrophy of type 2 fibers?
Steroid myopathy
What disease is associated with antibodies to the acetylcholine receptor?
Myasthenia gravis
What disease is associated with thymic hyperplasia, t
Type 2 atrophy, ptosis, diplopia, decreased motor response with repeated stimulation?
Myasthenia gravis
Who gets myasthenia gravis?
Women before 40
What is the treatment for myasthenia gravis?
Thymectomy
Prednisone
Plasmapheresis
Anticholinesterase agents
What develops as a paraneoplastic process?
Lambert eaton myasthenic syndrome
What disease has fewer vesicles synapse in response to an action potential?
Lambert eaton
What disease has enhanced neurotransmission with repeated stimulation?
Lambert eaton
What disease manifests as progressive muscle atrophy below the knee in childhood, palpable nerves and is autosomal dominant?
HMSN I
What is the most common mutation of HMSN I?
Mut in PMP22 - transmembrane protein in myelin
What disease has a mutation in KIF1B, is auto Dom and has no nerve enlargement?
HMSN II
What disease has depressed DTRs, auto recessive, palpable nerves, presents in early childhood?
Dejerine soltas neuropathy
What disease is auto recessive and destroys the anterior horn cells and CN motor neurons?
Spinal muscular atrophy
What is the mutation in spinal muscular atrophy?
SMN1 on ch.5 required for motor neuron survival
What is seen in spinal muscular atrophy?
Panfasciculad atrophy
Floppy baby
Death with first 3 years
