Neuro Flashcards
Cinchonism (drug reaction)
Quinidine
Quinine
Parkinson-like Syndrome (drug reaction)
Antipsychotics
Reserpine
Metoclopramide
Seizures (drug reaction)
Isoniazid (B6 deficiency)
Bupropion
Imipenem/cilastatin
Enflurane
Tardive dyskinesia (drug reaction)
Antipsychotics
Metoclopramide
Neural development
Notochord induces overlying ectoderm to differentiate into neuroectoderm and form neural plate
Neural plate gives rise to neural tube and neural crest cells
Notochord becomes nucleus pulposus of IV discs in adults
Alar plate (dorsal) = sensory (same as SC)
Basal plate (ventral) = motor (same as SC)
Regional specification of developing brain
1) Forebrain (prosencephalon)
- Branches into Telencephalon - Cerebral hemispheres and lateral ventricles
- Also into Diencephalon - Thalamus and 3rd ventricle
2) Midbrain (mesencephalon) - Midbrain and Aqueduct
3) Hindbrain - Metencephalon and Myelencephalon
- Metencephalon - Pons, Cerebellum, Upper part of 4th ventricle
- Myelencephalon - Medulla and lower part of 4th ventricle
CNS/PNS origins
Neuroectoderm - CNS, neurons, ependymal cells (inner lining of ventricles, make CSF), oligodendroglia, astrocytes
Neural crest - PNS neurons, Schwann cells
Mesoderm - Microglia (like Macrophages)
Neural tube defects
Neuropores fail to fuse (4th week) causing persistent connection between amniotic cavity and spinal canal
Associated with low folic acid intake before conception and during pregnancy.
Increased alpha-fetoprotein (AFP) in amniotic fluid and maternal serum
Increased acetylcholinesterase (AChE) in amniotic fluid is a helpful confirmatory test (fetal AChE in CSF transudates across defect into amniotic fluid)
Spina bifida occulta
Failure of bony spinal canal to close, but no structural herniation.
Usually seen at lower vertebral levels. Dura is intact. Associated with tuft of hair or skin dimple at level of bony defect. Normal AFP
Menigocele
Meninges (but no neural tissue) herniate through bony defect
Meningomyelocele
Meninges and neural tissue herniate through bony defect
Anencephaly
Forebrain anomaly
Malformation of anterior neural tube leads to no forebrain, open calvarium.
Clinical findings: High AFP; polyhydramnios (no swallowing center in brain)
Associated with maternal type 1 diabetes.
Maternal folate supplementation lowers risk
Holoprosencephaly
Forebrain anomaly
Failure of left and right hemispheres to separate; usually occurs during weeks 5-6
May be related to mutations in sonic hedgehog signaling pathway. Moderate form has cleft palate/lip, most severe form results in cyclopia.
Seen in Patau syndrome and Fetal Alcohol Syndrome
Chiari II
Posterior fossa malformation
Significant herniation of cerebellar tonsils and vermis through foramen magnum with aqueductal stenosis and hydrocephalus.
Often presents with lumbrosacral meningomyelocele, paralysis below the defet
Dandy-Walker
Posterior fossa malformation
Agenesis of cerebellar vermis with cystic enlargement of 4th ventricle (fills the enlarged posterior fossa)
Associated with hydrocephalus, spina bifida
Syringomyelia
Cystic cavity (syrinx) within spinal cord (if central canal - hydromyelia)
Crossing anterior spinal commissural fibers are typically damaged first. Results in a “cape-like” bilateral loss of pain and temperature sensation in upper extremities (fine touch sensation is preserved)
Associated with Chiari malformations, trauma, and tumors
Syrinx = tube, as in syringe
Most common at C8-T1
Chiari I malformation - cerebellar tonsillar ectopia > 3-5mm; congenital, usually asymptomatic in childhood, manifests with headaches and cerebellar symptoms
Tongue development
1st and 2nd branchial arches form anterior 2/3 (thus sensation via CN V3, taste via CN VII)
3rd and 4th branchial arches form posterior 1/3 (thus sensation and taste mainly via CN IX, extreme posterior via CN X)
Motor innervation is via CN XII to hypoglossus (retracts and depresses tongue), genioglossus (protrudes tongue), and styloglossus (draws sides of tongue upward to create a trough for swallowing)
Motor innervation is via CN X to palatoglossus (elevates posterior tongue during swallowing)
Taste - CN 7, 9, 10 (solitary nucleus)
Pain - CN V3, 9, 10
Motor - CN 10, 12
Neurons
Signal transmitting cells of the nervous system. Permanent cells - do not divide in adulthoos.
Signal-relaying cells with dendrites (receive input), cell bodies, and axons (send output)
Cell bodies and dendrites can be seen on Nissle Stain* (stains RER)
RER is not present in the axon.
Injury to axon leads to Wallerian degeneration - degeneration distal to injury and axonal retraction proximally; allows for potential regeneration of axon (if in PNS)
Astrocytes
Physical support, repair, K metabolism, removal of excess nt’s, component of BBB, glycogen fuel reserve buffer. Reactive gliosis in response to neural injury.
Astrocyte marker = GFAP
Derived from neuroectoderm
Microglia
Phagocytic scavenger cells of CNS (mesodermal, mononuclear origin)
Activated in response to tissue damage. Not readily discernible by Nissl stain
HIV-infected microglia fuse to form multinucleated giant cells in CNS
Myelin
Increases conduction velocity of signals transmitted down axons - saltatory conduction of action potential at the nodes of Ranvier, where there are high concentrations of Na channels.
CNS - oligodendrocytes
PNS - Schwann Cells
Wraps and insulates axons: Increases space constant and Increases conduction velocity
Schwann cells
Each Schwann cell myelinates only 1 PNS axon
Also promote axonal regeneration. Derived from neural crest
Increased conduction velocity via saltatory conduction at the nodes of Ranvier, where there is a high concentration of Na channels
May be injured in Guillain-Barre Syndrome
Acoustic Neuroma - type of schwannoma. Typically located in internal acoustic meatus (CN8). If bilateral, strongly associated with neurofibromatosis type 2
Oligodendroglia
Myelinates axons of neurons in CNS. Each oligodendrocyte can myelinate many axons (~30). Predominant type of glial cell in white matter
Derived from neuroectoderm
“Fried egg” appearance histologically
Injured in MS, progressive multifocal leukoencephalopathy (PML), leukodystrophies
Free nerve endings
C - slow, unmyelinated fibers
Adelta - fast, myelinated fibers
Location: All skin, epidermis, some viscera
Senses: Pain and temp