USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 1-day-old male infant is evaluated in the NICU for an increased cranial circumference. History reveals the patient was born via C-section at 40 weeks' gestation. Physical examination reveals a lethargic infant with bulging fontanels. A CT scan of the head is obtained and reveals the complete absence of the cerebellar vermis with cystic dilation of the fourth ventricle. Which of the following is his most likely diagnosis?
Dandy-Walker malformation, first described by Dr. Walter Dandy and Dr. Arthur Walker, is a congenital brain defect where there’s a cystic malformation in the cerebellum that blocks cerebrospinal fluid from exiting the brain.
The cerebellum, or "little brain", sits just below the main part of the brain and it’s divided at the midline into two hemispheres by a short worm-like structure called the vermis.
The cerebellum is contained within the back of the skull, in an area known as the posterior fossa, and it sits above the foramen magnum, an opening at the base of the skull through which the spinal cord enters.
The cerebellum controls balance and posture, and helps to initiate as well as fine-tune voluntary motor activity - think about the fancy finger work of a piano player or the vocal cords of a singer - that’s the cerebellum in action.
Highest up, are two C-shaped lateral ventricles that lie deep in each cerebral hemisphere.
In a Dandy-Walker malformation, there are three main defects.
- "Robbins Basic Pathology" Elsevier (2017)
- "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
- "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
- "CURRENT Medical Diagnosis and Treatment 2020" McGraw Hill Professional (2019)
- "The Most Common Comorbidities in Dandy-Walker Syndrome Patients: A Systematic Review of Case Reports" Journal of Child Neurology (2017)
- "Hydrocephalus in Dandy–Walker malformation" Child's Nervous System (2011)
- "Dandy-Walker malformation: prenatal diagnosis and prognosis" Child's Nervous System (2003)