USMLE STEP 1 Neurology Questions And Answers With Verified Updates
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Module
USMLE STEP 1 Neurology
Institution
USMLE STEP 1 Neurology
Propofol - Used for sedation in the ICU, rapid anesthesia induction, short procedures
LESS POST-OPERATIVE NAUSEA than thiopental
Potentiates GABAA
Holoprosencephaly - Failure of LEFT AND RIGHT HEMISPHERES TO SEPARATE
Usually occurs during the 5th and 6th week
May be related to mutations in the...
The Forebrain gives rise to: - 1. Telencephalon [Cerebral hemispheres, lateral ventricles]
2. Diencephalon [Thalamus, Third Ventricle]
The Midbrain gives rise to: - 1. Mesencephalon [Midbrain, aqueduct]
The Hindbrain gives rise to: - 1. Metencephalon [Pons, cerebellum, upper part of the fourth
ventricle]
2. Myelencephalon [Medulla, Lower part of the fourth ventricle]
CNS/PNS Origins - Neuroectoderm = CNS neurons, ependymal cell [Inner lining of ventricles,
makes CSF], oligodendrocytes, astrocytes
Neural crest cells = PNS, schwann cells
Mesoderm = Microglia [Like Macrophages, originate from Mesoderm]
Neural tube defects - NEUROPORES fail to fuse [4th week] → Persistent connection between
amniotic cavity and spinal canal
Associated with:
1. Low folate levels before conception and during pregnancy
2. ↑ a-fetoprotein levels [AFP] in amniotic and maternal serum
3. ↑ AChE in amniotic fluid [Helpful confirmatory test]
-- Fetal AChe in CSF transudates across defect into amniotic fluid
Spina bifida occulta - Failure of bony spinal canal to close, NO STRUCTURAL HERNIATION
Usually seen at lower vertebral levels
,DURA INTACT
Associated w/ tuft of hair or skin dimple at level of bony defect
NORMAL AFP
Meningocele - Meninges [BUT NO NEURAL TISSUES] herniates through bony defect
Meningomyelocele - Meninges and neural tissue herniate through bony defect
Associated w/ Arnold-Chiari Type II Malformation
Anencephaly - Malformation of the ANTERIOR NEURAL TUBE →
1. No forebrain
2. Open calvarium
Clinical Findings:
1. ↑ a-fetoprotein levels [AFP]
2. Polyhydramnios [No swallowing center in brain]
3. Associated w/ MATERNAL TYPE I DIABETES
4. Maternal folate supplementation ↓ risk
Chiari Type II Malformation - Posterior fossa malformation
Significant HERNIATION of the CEREBELLAR TONSILS and VERMIS through FORAMEN MAGNUM with
AQUEDUCTAL STENOSIS and HYDROCEPHALUS
Patients often present w/:
1. Lumbosacral meningomyelocele
2. Paralysis below the defect
Dandy-Walker Malformation - AGENESIS of CEREBELLAR VERMIS with CYSTIC ENLARGEMENT of
the 4th ventricle
Fills enlarged posterior fossa
, Associated w/:
1. Hydrocephalus
2. Spina bifida
Syringomyelia - Cystic cavity [Syrinx] within SPINAL CORD
If central canal = Hydromyelia
Crossing anterior spinal commissural fibers are typically damaged
CAPE-LIKE BILATERAL LOSS OF PAIN and TEMPERATURE in the UPPER EXTREMITIES
Fine touch sensation is preserved
Associated w/:
1. Arnold Chiari malformation
2. Trauma
3. Tumor
Most common C8-T1 [CERVICAL ENLARGEMENT]
Arnold Chiari Type I Malformation - CEREBELLAR TONSILLAR ECTOPIA > 3-5 mm
Congenital
Usually asymptomatic in childhood
Manifests w/ HEADACHE and CEREBELLAR SYMPTOMS
Which arches form the anterior 2/3rds of the tongue - 1st and 2nd brachial arches
-- Sensation via CN V
-- Taste via CN VII
Which arches form the posterior 1/3rd of the tongue - 3rd and 4th brachial arches
--Sensation and taste via CN IX
-- Extreme posterior vagus
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