Holoprosencephaly

It is a spectrum of fore brain disorders characterized by different degrees of frontal lobe fusion.

Alobar holoprosencephaly is when their is no interhemispheric fissure, single ventricle and basal ganglia and thalami are fused.

Semilobar holoprosencephaly is when the interhemispheric fissure is present posteriorly, basal ganglia, hypothalamus, caudate and thalami may be partially fused and there are partial formation of occipital and temporal horns.

"The face predicts the brain"

That means one can suspect it from various midline facial defects athat are often present including-

midline cleft, central incisor, absent superior frenulum, single nostril.

Seizures, dystonia and endocrine dysfunction is common. Posterior pituitary dysfunctions are more common than anterior pituitary deficiencies.

Workup includes high resolution chromosomal studies and HPE genetic mutations, electrolytes, cortisol, TSH, ACTH.

Recurrence risk is 6%. First trimester USG and fetal MRI can pick up holoprosencephaly.

SEGA-Subependymal giant cell astrocytoma

SEGA or sub ependymal giant cell astrocytomas are WHO grade I tumours often belived to have arisen from sub ependymal nodules. They grow into the ventricles and are often near the Foramen of Munro. They may remain asymptomatic or as they slowly enlarge produce obstructive hydrocephalus.

CT findings- are iso or heteroeintense with grey matter and enhance with contrast. Often larger than 1 cm

MR findings- 

• T1 : heterogenous and hypo to iso intense to grey matter 
• T2 : heterogenous and hyper intense to grey matter ; calcific components can be hypo intense
• T1 C+ (Gd) : can show marked enhancement

 Treatment options: Surgical resection . May sometimes recur if not fully resected.

Everolimus is a drug which has shown to reduce the size of SEGA's.

It acts by inhibiting the m TOR complex 1which are normally inhibited by the TSC1 and TSC 2 gene missing in tuberous sclerosis.