Fetal Brain Anomalies Part III Holoprosencephaly HPE Severe

Fetal Brain Anomalies Part III Holoprosencephaly HPE 洪正修主任楊明智主任指導陳志堯醫師

Severe brain malformation due to early arrest in brain cleavage and rotation.

Five Cephalons 9+ wks Prosencephalon Rhombencephalon

5 th wk Telencephalon Prosencephalon (forebrain) Diencephalon Neural tube & folds 3~4 th wk 1. 2. 3. 4. Cerebral hemisphere Choroid plexus Internal capsule Olfactory bulbs and tracts 1. 2. 3. 4. Thalamus Optic nerve Geniculate & mamillary body Pineal and pituitary glands Mesencephalon (midbrain) Metencephalon Pons, cerebellum Rhombencephal on (hindbrain) Myelencephalon Medulla

Three Types of HPE Alobar Semi-lobar Lobar

Classification & Features of Holoprosencephaly Classification Features Alobar (most common in uterus) Fused thalami Facial abnormalities Mono-ventricular cavity Absent falx cerebri Fused thalami. Facial abnormalities, Mono-ventricular cavity with increased cerebral tissue, especially in the occipital lobes Squared frontal horns Absent cavum septi pellucidi ± ventriculomegaly Otherwise fairly normal intracranial anatomy Semi-lobar (rarest form) Lobar (usually identified in infants)

Alobar Holoprosencephaly

Nomenclature for associated facial malformations. Cyclopia (獨眼畸形併眼畸形) Ethmocephaly (篩形頭畸胎形) Cebocephaly (猴頭畸胎形) Face with median cleft lip

Best Diagnostic Clues 1 st trimester Absent of butterfly sign: Abnormal appearance of choroid plexus 2 nd~3 rd trimester Fused thalami with mono-ventricle

Ultrasound Findings Absence of butterfly sign Single ventricle Absent midline structures Fused thalami Dorsal sac Remaining brain has 3 appearance Pancake, Cup, Ball

Ultrasound Obstet Gynecol 2000; 15: 62– 65

Prenat. Diagn. 19: 859– 862 (1999)

CY Chen 2007

Ultrasound Findings Absence of butterfly sign Single ventricle Absent midline structures Fused thalami Dorsal sac Remaining brain has 3 appearance Pancake, Cup, Ball

Ultrasound Findings Absence of butterfly sign Single ventricle Absent midline structures Fused thalami Large dorsal sac Remaining brain has 3 appearance Pancake, Cup, Ball

Large dorsal sac

Ultrasound Findings Absence of butterfly sign Single ventricle Absent midline structures Fused thalami Large dorsal sac Remaining brain has 3 appearance Pancake, Cup, Ball

Pathology Most sporadic Trisomy 13, 18, triploid, monosomy 21 At least 12 different genes involved in HPE 1: 16000 births，1: 250 in terminated preg. Facial malformations of any kind should trigger a very careful of the brain

Semi-lobar Incomplete interhemispheric fissure Rudimentary cerebral lobes Olfactory tracts and bulbs absent or hypoplastic Abnormal corpus callosum Thalami completely/partly fused

Lobar HPE Interhemispheric fissure present Well formed cerebral lobes Abnormal corpus callosum Thalami normal/partly fused Fornices fused Abnormal ACA