Neonatal Head Pathology Study Notes

NEONATAL HEAD PATHOLOGY

Overview

  • Objective: Recognize, identify, and appropriately document abnormal patterns of disease processes, pathology, and pathophysiology of the neonatal brain.
  • Clinical Correlation: Correlate basic laboratory values and clinical history with neonatal pathology related to the neonatal brain.
  • Sonographic Findings: Discuss the sonographic findings in neonatal brain pathology.
  • Imaging Modalities: List other imaging modalities that may be utilized to examine neonatal head pathology.

BRAIN PATHOLOGY

CHIARI MALFORMATIONS
  • Key Signs:
    • A. Lemon sign
    • B. Banana sign
    • C. Ventriculomegaly
    • D. Normal ventricles
Definition:
  • Chiari Malformation: Caudal displacement of cerebellum without displacement of the 4th ventricle.
Types:

  1. Chiari I:

    • Caudal displacement of cerebellum.
    • No displacement of the 4th ventricle or medulla.

  2. Chiari II (Most Common):

    • Elongation and caudal displacement of the brainstem and cerebellum through the foramen magnum.
    • Associated with meningomyelocele.
Sonographic Findings for Chiari II:
  • Small posterior fossa.
  • Small, displaced cerebellum.
  • Widening of the 3rd ventricle.
  • Possible myelomeningocele formation.
  • Decompression of ventricles.
  • May be asymptomatic at birth and only cause issues with growth.
Chiari Malformation Type I Findings:
  • Cerebellar tonsils & vermis herniated into the spinal canal through the enlarged foramen magnum.
  • Pons & medulla inferiorly displaced.
  • 4th ventricle becomes elongated.
  • Possible enlargement of massa intermedia.
  • 3rd ventricle may be slightly enlarged.
Comparing Chiari Malformations:
  • Chiari I vs. Chiari II:
    • Chiari I: Downward displacement of cerebellar tonsils.
    • Chiari II: Downward displacement of cerebellum, brainstem, and fourth ventricle.
  • Syringomyelia: Can occur with Chiari malformations where cysts form in the spinal cord.
  • Hydrocephalus: Characterized by cerebrospinal fluid build-up, needing distinct imaging and management.
Types of Chiari Malformations:
  1. Chiari III: Rare; cervical encephalomeningocele containing cerebellum, 4th ventricle & medulla.
  2. Chiari IV: Rare; most severe form; severe hypoplasia of cerebellum without displacement.
HOLOPROSENCEPHALY
Definition:
  • A congenital anomaly characterized by the grossly abnormal brain with a common large central ventricle due to the failure of cleavage of the prosencephalon into separate cerebral hemispheres.
Forms:
  1. Alobar
  2. Semilobar
  3. Lobar
  • Characteristics:
    • Alobar: Thin mantle of brain tissue; surrounds horseshoe monoventricle; fused thalami anterior to fused choroid plexus; absence of falx, interhemispheric fissure, corpus callosum, and 3rd ventricle.
    • Semilobar: Single midline ventricle; posterior portion of falx & interhemispheric fissure present; absent or incomplete corpus callosum; possible partial separation of ventricle.
    • Lobar: Near complete separation of hemispheres; development of falx & interhemispheric fissure; only frontal lobes fused; septum pellucidum is absent.
DANDY-WALKER MALFORMATION (DWM)
Definition:
  • Congenital anomaly of the roof of the 4th ventricle concurrent with occlusion of the aqueduct of Sylvius and foramina of Magendie & Luschka.
  • Features anomalies in the posterior fossa with dysgenesis of the cerebellar vermis, dilatation of the 4th ventricle, and enlargement of the posterior fossa.
Classification:
  • Small vermis, rotation of vermis, and big posterior fossa in classic Dandy-Walker Malformation.
  • Cerebellar Vermis Megacisterna Hypoplasia (CVH): Small vermis with no rotation.
  • Magna: Normal vermis with no rotation and a normal posterior fossa but a big posterior fossa.
Sonographic Appearance of Dandy-Walker Malformation:
  • Enlarged 4th ventricle cyst occupies an area of cerebellum.
  • Widening of 3rd and lateral ventricles.
  • Possible absent vermis leading to hydrocephalus.
CALLOSAL DYSGENESIS (Agenesis of Corpus Callosum)
Definition:
  • Complete or partial absence of connective tissue between cerebral hemispheres.
  • Can be an isolated finding or associated with other anomalies.
Sonographic Appearance:
  • Marked lateral ventricular separation with parallel configurations.
  • Widening of occipital horns & 3rd ventricle.
  • Appearance described as "longhorn" or "moose head" with gyri appearing in straightened "sunray" or "sunburst" appearance.
VENTRICULOMEGALY
General Definition:
  • Enlargement (unilateral or bilateral) of ventricles without an increase in head circumference.
Causes:
  • Neural tube defects, Dandy-Walker malformations, Lissencephaly, cytomegalovirus (CMV) infections, vein of Galen aneurysm.
Types:
  1. Communicating: CSF flow not obstructed between ventricles and subarachnoid cisterns.
  2. Non-communicating: CSF flow is blocked.
HYDROCEPHALUS
General Definition:
  • Enlargement (unilateral or bilateral) of ventricles with increased head circumference.
Causes:
  1. Communicating Hydrocephalus:
    • Impaired CSF absorption or increased production; causes include neural tube defects, Chiari malformations, choroid papilloma.
  2. Non-Communicating Hydrocephalus:
    • External compression or intraventricular obstruction; causes include congenital aqueductal stenosis, obstruction due to clots, compression from lesions.
Signs of Increased Intracranial Pressure:
  • Bulging anterior fontanelle.
  • Lethargy, irritability, hemiparesis, convulsions.
Sonographic Appearance of Hydrocephalus:
  • Blunted lateral angles of enlarged lateral ventricles.
  • Possible rupture of interhemispheric fissure.
  • Thinned brain mantle with enlarged head circumference, with possible obstruction points visible in non-communicating hydrocephalus.