Peripheral Nerve and Skeletal Muscle Path Flashcards
Segmental Neuropathy
Etiologies (2) Unaffected Structures (2) Characteristic Morphology (1)
Schwann cell dysfunction
Direct damage to myelin sheath
Axon and Myocytes untouched
Onion bulb concentric layers of Schwann cytoplasm
Axonal Neuropathies
Morphology (2) Complication with Description (2)
Wallerian degeneration Myelin ovoids (degrading myelin sheath)
Traumatic neuroma
Painful pseudotumor
Disordered orientation of regrowing axons
Nerve Regeneration and Muscle Reinnervation Process Early Compensation (2) Muscle Typing
Unaffected axons reinnervate denervated myocytes
Form new motor unit, adhering to type grouping
Motor neuron determines type of muscle fiber
Muscle Fiber Atrophy
Etiologies (4) Morphology (2)
Reactions (2) with Descriptions (2/1)
Regeneration Characteristics (3)
Denervation (group atrophy)
Neurodegenerative diseases
Inactivity
Glucocorticoid therapy
Angulated Fibers
Target Fibers
Segmental necrosis: myophagocytosis followed by collagen and fat deposition
Hypertrophy: muscle fiber splitting
Regeneration:
Red cytoplasm
Central nuclei
Stains basophilic
Mononeuritis Multiplex
Etiologies (2) Description
Vasculitis (polyarteritis nodosa)
HIV
Nerves damaged in haphazard fashion
Peripheral Nerve Damage
Common Symptom
Anatomic Variants with Descriptions
Mono (1) Poly (3) Polyradiculo (2)
Pins and needles pain
Mononeuropathy affects single nerve
Polyneuropathy: multiple nerves
Symmetric Ascending symptomology
Glove and stocking distribution
Polyradiculoneuropathy: multiple nerves and nerve roots
Symmetric proximal and distal symptomology
Bell’s Palsy
Etiology, Associations (2) Presentation
CN VII mononeuropathy
Upper respiratory infection
Diabetes mellitus
One sided face droop
Neurogenic Bladder Disease Associations (4)
Multiple sclerosis
Parkinson’s Disease
Spina Bifida
Diabetes
Guillain-Barre Syndrome
Etiologies (2) Pathogenesis (2) Morphology (4) Presentation (2) CSF Finding (1) Treatment (2)
Influenza-like illness
Campylobacter jejuni
Anti-myelin Abs
Macrophages attack Schwann cells at nodes of ranvier
Perivenular and endoneurial inflammatory infiltrate
Segmental demyelination of nerves and nerve roots
Ascending paralysis starting in distal LE
Loss of DTR’s
Elevated Protein in CSF
Plasmapharesis
IV Ig
Chronic Inflammatory Demyelinating Polyradiculoneuropathy Clinical Features (3) Morphology
Symmetrical mixed sensorimotor neuropathy
Lasts > 2 months
Responsive to corticosteroids
Onion bulb Schwann cells
Leprosy
Pathogenesis (3) Morphology (2) Clinical Features (3) Staining (1)
Schwann cells invaded by Mycobacterium leprae
Segmental demyelination/remyelination
Loss of myelinated and unmyelinated axons
Endoneurial fibrosis
Thickened perineural sheaths
Symmetrical polyneuropathy of cool extremities
Loss of pain sensation
Large traumatic ulcers
(+) AFB staining
Diphtheria
Pathogenesis (3) Clinical Features (3)
Exotoxin mediated
Selective demyelination of axons going to anterior/posterior root and sensorimotor nerves
Early paresthesias and weakness
Bulbar and respiratory dysfunction
Tonsillar exudate
Diabetic Peripheral Neuropathy
Pathogenesis (3) Morphology (3) Clinical Features (4)
Segmental demyelination
Loss of small myelinated fibers and unmyelinated fibers
Decreased axons
Thickened, hyalinized, PAS (+) endoneurial arterioles
Ascending distal symmetric sensorimotor polyneuropathy
Paresthesias
Dysthesias
Autonomic Dysfunction (postural hypotension)
Uremic Neuropathy
Etiology and Clinical Features (2)
Renal failure
Distal symmetric neuropathy
Healed by dialysis
Thyroid Associated Neuropathy
Hyper (1) Hypo (2)
Hyperthyroidism causes Guillain-Barre-like syndrome
Hypothyroidism causes compression neuropathies
Carpal tunnel
Malignant Neuropathies
Paraneoplastic (2)
B cell Neoplasms: Pathogenesis, Presentation (5)
Sensorimotor paraneoplastic syndrome
Small cell lung carcinoma
B Cell Neoplasms:
Deposition of paraprotien between noncompacted myelin lamellae
POEMS: polyneuropathy, organomegaly, endocrinopathy, Monoclonal gammopathies, skin changes
Compression Neuropathies
Syndromes (3) with Entrapped Nerve
Other Commonly Entrapped Nerves (2)
Carpal Tunnel: Median N
Saturday Night Palsy: Radial N
Morton Neuroma (metatarsalgia): Interdigital N
Ulnar N
Peroneal N
Charcot-Marie Tooth
Genetics (3) Presentation (2)
Autosomal Dominant
Chr 22 mutation
PMP22 defect
Slowly progressive demyelination starting in second decade
Myasthenia Gravis
Etiology, Clinical Features (5) Treatments (3)
Ach receptor autoantibodies
Diplopia Ptosis Worsened by activity, repeated stimulation Thymic Hyperplasia (B cells on histo) Thymoma
Acetylcholinesterase inhibitors
Immunosuppression or plasmapharesis
Thymectomy
Lambert Eaton Syndrome
Etiology, Pathogenesis (2) Presentation (2)
Paraneoplastic syndrome of small cell lung carcinoma
Autoantibody to Ca2+ channel
Blocks acetylcholine release
Proximal muscle weakness
Improved by activity, repeated stimulation
Muscle Fiber Type Characteristics
Action, Activity Type, Specialization
Type I, Type II
Type I:
Sustained force
Aerobic exercise
High resistance to fatigue
Type II:
Fast movement
Anaerobic exercise
High power production
Dermatomyositis
AutoAbs (3) Morphology (3) Clinical Features (3) Histology, Complications (4)
anti-Mi2
anti-Jo1
anti-P155/P140
Upper eyelid rash* (lilac/heliotrope/violet)
Telangiectasias causing rash and periorbital edema
Grotton lesions: scaly, on knuckle/elbows/knees
Proximal muscle weakness (trouble walking up stairs)
Dysphagia
Interstitial lung disease
Perifascicular atrophy*
Visceral cancer
GI ulcers (juvenile)
Calcinosis (juvenile)
Lipodystrophy (juvenile)
Polymyositis
Pathogenesis, Morphology(2) Clinical Features (3)
CD8+ T cell mediated inflammation (mononuclear infiltrate)
Endomysial inflammation*
Random fiber atrophy*
Adult onset
Myalgias
Proximal limb weakness
Inclusion Body Myositis Clinical Features (3) Morphology
Slow progressive muscle weakness
Quadriceps and Distal Upper Extremities most affected
Dysphagia
Rimmed vacuole inclusions
Toxic Myopathies
Examples (5) with Descriptions
Statins
Chloroquine and Hydroxychloroquine
Corticosteroids
Thyrotoxic: proximal muscle weakness
Alcohol: Rhabdomyolysis, renal failure
X Linked Muscular Dystrophies
Common Genetic Defect and Common Morphology
Duchenne Features (3)
Becker Features (3)
Xp21 gene mutation
Pseudohypertrophy: muscle replaced with Adipose, CT
Duchenne: Dystrophin absent
Early symptoms and wheelchair bound by 10 years
Females are carriers
Becker: Dystrophin decreased
Normal lifespan
Cardiac disease
Myotonic Dystrophy
Genetics (3) Clinical Description (2) Symptoms (5) Morphology
Autosomal dominant
CTG repeat
DMPK defect
Sustained involuntary contraction of muscles
Myotonia elicited by percussion of thenar eminence
Ptosis Hatchet face Cataracts Endocrinopathy Cardiomyopathy
Ring fibers
Emery Dreifuss Syndrome
Genetics (2) Clinical Triad
X linked: EMD1
Autosomal Dominant: EMD2
Slowly progressive weakness
Cardiomyopathy
Early contractures
Lipid/Glycogen Metabolism Defects Common Symptomology (2) Examples with Defects (3)
Slowly progressive muscle damage
Symptoms show with exercise and fasting
Carnitine Palmitoyltransferase II deficiency
McArdle Disease: myophosphorylase deficiency
Pompe Disease: Acid Maltase deficiency
Mitochondrial Myopathies
Common Clinical Features (3) Examples (4) Common Morphology (2)
Increased Creatine Kinsae
Rhabdomyolysis
Extraocular Muscle Defects
Leber Optic Neuropathy
Leigh syndrome
Barth syndrome
Kearns-Sayer syndrome
Ragged red fibers
Paracrystalline parking lot inclusions
Spinal Muscular Atrophy
Genetics (3) Pathogenesis, Morphology, Wernig Hoffman Syndrome (5)
Autosomal recessive
Chromosome 5 mutation
SMN1 defect
Loss of motor neurons in the Anterior Horn
Panfascicular atrophy
Floppy baby* Truncal and extremity weakness Dysphagia Dsypnea Death by age 3
Malignant Hyperthermia
Mutation, Pathogenesis, Symptoms (3) Antidote
RYR1 mutation
Anesthesia triggers increased Calcium release causing hypermetabolic state
Hyperpyrexia
Tachycardia
Muscle spasms
Dantrolene
Tuberous Sclerosis
Genetics (3) Clinical Features (8)
Autosomal dominant
TSC1: Hamartin defect (Chr 9q34)
TSC2: Tuberin defect (Chr 16p13)
Hamartomas Renal Angiomyolipomas Pulomary Lymphangioleiomyomatosis Cardiac Rhabdomyomas Angiofibromas Subungual fibromas Shagreen patches Ash-leaf patches
Von Hippel Lindau Disease
Genetics (3) Clinical Features (5)
Autosomal Dominant
Chromosome 3 mutation
VHL defect
Polycythemia CNS/Retinal Hemangioblastomas Cysts Renal cell carcinoma Pheochromocytoma
Neurofibromatosis
Clinical Features Type 1 (4) Type 2 (3)
Mutations Type 1 and Type 2
Type 1: Chr 17 mutation (neurofibromin) Neurofibromas (plexiform can become MPNST) Optic N gliomas Lisch nodules in iris Cafe au Lait spots
Type 2: Chr 22 mutation (merlin)
Bilateral CN VIII Acoustic Neuromas (schwannomas)
Meningiomas
Ependymomas
