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USMLE STEP 1 Neurology Questions And Answers With Verified Updates

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  • USMLE STEP 1 Neurology
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  • 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...

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  • August 17, 2024
  • 86
  • 2024/2025
  • Exam (elaborations)
  • Questions & answers
  • USMLE STEP 1 Neurology
  • USMLE STEP 1 Neurology
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ACADEMICMATERIALS
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 SONIC HEDGEHOG signaling pathway

Moderate form = Cleft lip/palate

Severe form = Cyclopia

Seen in:

1. PATAU SYNDROME

2. FETAL ALCOHOL SYNDROME




Neural plate then gives rise to? - Neural tube and neural crest cells



Notochord becomes what? - Nucleus pulposus of the intervertebral disks in adults



Alar Plate - Dorsal [Sensory]

Same orientation as spinal cord



Basal Plate - Ventral [Motor]

Same orientation as the spinal cord



How does FGF affect chordin and noggin? - FGF regulates chordin and noggin to down regulate
BMP which leads to neural plate induction

,Three Primary Vesicles - 1. Forebrain [Prosencephalon]

2. Midbrain [Mesencephalon]

3. Hindbrain [Rhombencphaln]



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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