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Flashcards in Neuro Deck (229)
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151

Subacute Sensory Neuropathy

  • paraneoplastic syndrome.
  • can be with limbic encephalitis.
  • marked by dorsal root ganglia inflammation and neuronal loss.

152

Schwannoma

  • benign tumor of schwann cells.
  • associated with vestibular branch of CN VIII at cerebellopontine angle (vestibular schwannoma or acoustic neuroma).
    • have tinnitus and hearing loss.
  • extradural = associated with large nerve trunks.
  • inactivating mutation of NF2 ⇒ loss of merlin ⇒ hyperproliferation
  • morphology: well-circumscribed encapsulated firm gray masses with cystic and xanthomatous changes.
    • attached to nerve but separable.
    • spinal tumors from dorsal roots, extend through vertebral foramen = dumbbell shape.
    • Antoni A = elongated cells with cytoplasmic processes, arranged in fascicles in areas of mod-high cellularity with little stromal matrix.
    • Antoni B = less densely cellular tissues with microcysts and myxoid changes.
    • basement membrane deposition encasing single cells and collagen fibers.

153

Neurofibroma

  • discrete localized mass.
  • skin lesions = nodules.  can be large and pedunculated.
  • plexiform neurofibromas = infiltrating lesion that expands peripheral nerve.
    • loss of both NF1 genes ⇒ ↓ RAS GTPase, ↑ RAS function
  • can't separate from nerve.
  • loose myxoid background, low cellularity.
  • NF1 = multiple or plexiform lesions
    • diffucult to remove from nerve, ↑ risk malignancy.

154

Malignant Peripheral Nerve Sheath Tumors

  • highly malignant, locally invasive sarcomas.
  • de novo or from plexiform neurofibroma transformation (NF1).
  • ill-defined mass infiltrating parent nerve and adjacent soft tissue.
  • resembles schwann cells.  fascicle formation, mitosis, necrosis, anaplasia.

155

Cowden Syndrome

  • dysplastic cerebellar gangliocytomas
  • due to PTEN mutation.

156

Li-Fraumeni Syndrome

  • medulloblastoma from p53 mutation

157

Turcot Syndrome

  • medulloblastoma or glioblastoma
  • APC or mismatch repair gene mutation

158

Gorlin Syndrome

  • medulloblastoma from PTCH mutation

159

Neurofibromatosis Type 1

  • autosomal dominant.
  • neurofibromas (cutaneous and plexiform), optic nerve gliomas, meningiomas, pigmented nodules of iris (Lisch nodules), and cutaneous hyperpigmented macules (café au lait spots)
  • can be disfiguring, create spinal deformities.
  • lack neurofibromin from biallelic gene inactivation (NF1).

160

Neurofibromatosis Type 2

  • autosomal dominant.
  • inactivation of NF2.
  • form bilateral CN VIII schwannomas or multiple meningiomas.

161

Tuberous Sclerosis Complex

  • autosomal dominant
  • angiofibromas, seizures, mental retardation.
  • hamartomas include cortical tubers = haphazardly arranged neurons and cells expressing phenotypes intermediate btw glia and neurons; subendymal hamartomas = large astrocytic and neuronal clusters forming subependymal giant cell astrocytomas
  • can have renal angiomyolipomas, retinal glial hamartomas, cardiac rhabdomyomas, pulmonary lymphangioleiomyomatosis
  • cutaneous lesions = angiofibromas, shagreen patches (leathery thickenings), sunungual fibromas, hypopigmented areas (ash-leaf patches)
  • TSC1 encodes hamartin.
  • TSC2 encodes tuberin
  • TSC1 and TSC2 form complex that inhibits mTOR kinase ⇒ ↑ mTOR activity ⇒ ↑ protein synthesis and ↑ cell size.

162

Von Hippel-Lindau Disease

  • autosomal dominant
  • causes hemangioblastomas in cerebellum, retina, or brainstem and spinal cord.  cysts in pancreas, liver, and kidney.
  • propensity for renal cell carcinoma and pheochromocytomas.
  • mutated VHL ⇒ dysregulated HIF-1 ⇒ ↑ expression VEGF, erythropoietin, other growth factors.
    • VHL encodes part of ubiquitin-ligase complex that downregulates HIF-1.

163

Epineurium

  • encases all fascicles of entire nerve

164

Perineurium

  • encases each fascicle

165

Endoneurium

  • surrounds individual nerve fibers.

166

Anterior Spinal Root

  • has motor fibers

167

Posterior Spinal Root

  • has sensory fibers

168

Type 1 Muscle Fiber

  • mneumonic: 'one slow fat red ox'
    • ONE: type 1
    • SLOW: twitch, sustained force, weight bearing.
    • FAT: lipid-rich.
    • RED: color is red.
    • OX: oxidative, many mitochondria.
  • ex. soleus

169

Type 2 Muscle Fiber

  • for sudden, purposeful movements
  • type 2 fiber
  • fast-twitch
  • few lipids, abundant glycogen
  • white color
  • anaerobic: few mitochondria, narrow Z-band.
  • ex: pectoral

170

Segmental Demyelination

  • from schwann cell dysfunction or myelin sheath damage.  axon is normal.
  • denuded axons stimulate remyelination, precursor cells in endoneurium replace injured schwann cells.
    • internode distances shorter, myelin sheath thinner.
  • onion bulbs = recurrent demyelination and remyelination causes layers of Schwann cell processes.
  • chronic demyelinating disorders ⇒ axonal injury.

171

Wallerian Degeneration

  • rxn distal to a transected axon.
  • reflects axonal and myelin breakdown with macrophage recruitment and phagocytosis.
  • proximal uninjured nerve may have focal degeneration of distal 2-3 internodes before regenerative activity.

172

Denervation Atrophy

  • in muscle fibers of affected motor unit.
  • myocytes smaller and more angular but still viable.

173

Nerve Regeneration

  • proximal stump regrows 1mm/day.
  • guided by Schwann cells.

174

Reinervation of Muscle

  • neighboring motor units extend sprouts and incorporate muscle fibers into healthy motor unit.
    • get fiber type of the new innervating neuron ⇒ type grouping.
    • injury of nerve innervating the type grouping patch ⇒ group atrophy.
  • type 2 fiber atrophy = disuse atrophy
    • see in corticosteroid myopathy

175

Segmental Necrosis of Muscle Fiber

  • myofiber damage followed by myophagocytosis from infiltrating macrophages.
  • fibers replaced with collagen and fat.

176

Regeneration of Muscle Fiber

  • satellite cells proliferate to reconstitute fibers.
  • new fibers have large internalized nuclei, prominent nucleoli, basophilic cytoplasm laden with RNA.

177

Hypertrophy of Muscle Fibers

  • ↑ load ⇒ enlarged fibers

  • muscle fiber splitting = divide longitudinally

    • one large fiber with central membrane, have adjacent nuclei.

178

Guillain-Barré Syndrome

  • aka acute inflammatory demyelinating polyradiculoneuropathy
  • acute life-threatening ascending paralysis.
  • pathogenesis: immune-mediated.  60-70% preceded by vaccination or viral/bacterial infection.
    • viral = EBV, CMV
    • bacterial = Campylobacter, Mycoplasma
    • T cells or circulating Ab ⇒ demyelination.
  • morphology: segmental demyelination with chronic inflammation involving nerve roots and peripheral nerves.
    • severe = axonal damage.
  • presentation: muscle weakness, loss of deep tendon reflexes.
    • begins in distal limbs, rapidly includes proximal.
    • nerve conduction velocity slowed.
    • CSF protein ↑.  no pleocytosis.
    • death in 2-5% from respiratory paralysis, autonomic instability, or cardiac arrest.
    • 20% permanent disability.

179

Chronic Inflammatory Demyelinating Polyradiculoneuropathy

  • mixed sensorimotor neuropathy similar to Guillain-Barré.
  • has relapses and remissions.
  • have onion bulbs.

180

Leprosy

  • aka Hansen's Disease.
  • by M. leprae invading Schwann cells.  then proliferate and infect other cells.
  • causes segmental demyelination and remyelination, axonal loss, endoneurial and epineurial fibrosis.
  • lepromatous: disease more severe and diffuse.  symmetric polyneuropathy in extremities.
    • predilection for pain fibers ⇒ don't feel pain, get large ulcers.
  • tuberculous: nodules of granulomatous inflammation, localized nerve injury.