USMLE STEP 1 Neurology Exam Questions With Correct Answers
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Course
USMLE
Institution
USMLE
USMLE STEP 1 Neurology Exam Questions
With Correct Answers
The notochord induces what to differentiate into what? - answerInduces overlying
ECTODERM to differentiate into NEUROECTODERM and form NUERAL PLATE
Neural plate then gives rise to? - answerNeural tube and neural crest cells
Notochord b...
The Forebrain gives rise to: - answer✔✔1. Telencephalon [Cerebral hemispheres, lateral
ventricles]
2. Diencephalon [Thalamus, Third Ventricle]
The Midbrain gives rise to: - answer✔✔1. Mesencephalon [Midbrain, aqueduct]
The Hindbrain gives rise to: - answer✔✔1. Metencephalon [Pons, cerebellum, upper part of the
fourth ventricle]
2. Myelencephalon [Medulla, Lower part of the fourth ventricle]
Neural tube defects - answer✔✔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 - answer✔✔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 - answer✔✔Meninges [BUT NO NEURAL TISSUES] herniates through bony
defect
Meningomyelocele - answer✔✔Meninges and neural tissue herniate through bony defect
Associated w/ Arnold-Chiari Type II Malformation
Anencephaly - answer✔✔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
Holoprosencephaly - answer✔✔Failure of LEFT AND RIGHT HEMISPHERES TO
SEPARATE
Usually occurs during the 5th and 6th week
May be related to mutations in the SONIC HEDGEHOG signaling pathway
Moderate form = Cleft lip/palate
Severe form = Cyclopia
Seen in:
1. PATAU SYNDROME
2. FETAL ALCOHOL SYNDROME
Chiari Type II Malformation - answer✔✔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 - answer✔✔AGENESIS of CEREBELLAR VERMIS with
CYSTIC ENLARGEMENT of the 4th ventricle
Fills enlarged posterior fossa
Associated w/:
1. Hydrocephalus
2. Spina bifida
Syringomyelia - answer✔✔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/:
Arnold Chiari Type I Malformation - answer✔✔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 - answer✔✔1st and 2nd brachial arches
-- Sensation via CN V
-- Taste via CN VII
Which arches form the posterior 1/3rd of the tongue - answer✔✔3rd and 4th brachial arches
--Sensation and taste via CN IX
-- Extreme posterior vagus
Motor innervation of the tongue - answer✔✔CN XII [Hypoglossal nerve] to:
1. Hyoglossus = Retracts and depresses tongue
2. Genioglossus = Protrudes tongue
3. Styloglossus = Draws sides of tongue upward to create a trough for swallowing
CN X [Vagus] to:
1. Palatoglossus = Elevates posterior tongue during swallowing
Neurons - answer✔✔Signal-transmitting cells of the nervous system
Permanent cells = DO NOT DIVIDE IN ADULTHOOD
Signal relaying cells w/ dendrites [Receive input], cell bodies, and axons [Send output]
CELL BODIES AND DENDRITES CAN BE SEEN ON NISSLE STAINING [Stains RER]
RER is not present in an axon
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