Neurology

Question 1

describe spina bifida occulta

Answer 1

• results from failure of the embryonic halves of the neural arch to grow normally and fuse in the median plane
• in its most minor form, the only evidence of its presence may be a small dimple with a tuft of hair arising from it

Question 2

describe spina bifida cystica

Answer 2

• severe types of spina bifida, involving protrusion of the spinal cord, the meninges, or both through the defect in the vertebral arches, are referred to as spina bifida cystica
• when the sac contains meninges and CSF, the anomaly is called spina bifida with meningocele; if the spinal cord, nerve roots or both are included, it is called spina bifida with meninomyelocele

Question 3

describe cranium bifidum

Answer 3

• the defect is often in the squamous part of the occipital bone and may include the posterior part of the foramen magnum
• when the defect is small, usually only the meninges herniate, and is called a cranial meningocele; if the protruding brain contains part of the ventricular system, the anomaly is called a meningohydroencephalocele

Question 4

describe meroencephaly (aka anencephaly)

Answer 4

• results from failure of the rostral neuropore to close
• as a result, the forebrain primordium is abnormal and development of the calvaria is defective; in such cases, most of the infant’s brain extrudes from the cranium, known as exencephaly
• polyhydramnios is often associated with this because the fetus lacks the neural control for swallowing amniotic fluid

Question 5

describe Arnold-Chiari malformation

Answer 5

• ACM is the most common congenital anomaly involving the cerebellum
• a tonguelike projection of the medulla and inferior displacement of the vermis of the cerebellum herniate through the foramen magnum into the vertebral canal
• this condition results in a type of communicating hydrocephalus in which there is interference with the absorption of CSF; as a result, the entire ventricular system is distended