Sunday, September 7, 2008

Parts of the sylvian fissure



The sylvian fissure divides the frontal lobe and parietal lobe above from the temporal lobe below.

Sylvian fissure has two parts.

1. Superficial part

2. Deep part

The superficial part is the part seen to the exterior

The convexity face of the Sylvian fi ssure displays fi ve major arms (rami) that help to define the surface anatomy of the convexity.

The long nearly horizontal portion of the sylvian fi ssure is the posterior horizontal ramus (PHR).

At its anterior end, the anterior horizontal ramus (AH) and the anterior ascending (AA) ramus arise together in a “V” or “Y” confi guration.

At its posterior end, the prominent posterior ascending (PA) ramus and the small posterior descending (PD) ramus branch outward in a “T” or “fi shtail” confi guration.

The anterior subcentral sulcus ( Single arrow) and the posterior subcentral sulcus (Double arrow) form two minor arms that extend superiorly into the frontoparietal operculum to delimit the subcentral gyrus.

One or multiple transverse temporal sulci (Triple arrows) extend inferiorly into the temporal lobe in relation to the transverse temporal gyrus of Heschl.

The deep part has 2 compartments

1. The Spheniodal or Anterior compartment and

2. Operculo insular or Posterior compartment



Thursday, September 4, 2008

CT findings in ventriculomegaly

Ventriculomegaly secondary to atrophy

1.  Frontal angle is obtuse

2. widened sulci and cisterns

Ventriculomegaly secondary to NPH

1. ventriculomegaly out of proportion to sulcal enlargement

2. size of the hippocampus is normal and it distingushes ventriculomegaly with NPH to ventriculomegaly secondary to atrophy

Imaging of Hydrocephalus

1. The ratio between the largest width of the frontal horns and the internal diameter from inner-table to inner-table at this level should be greater than 0.5 in the presence of hydrocephalus.

2. Evan's ratio : Ratio of the largest width of the frontal horns to maximal biparietal diameter  is greater than 30% in acute hydrocephalus.

3. Acute frontal angle

4. Temporal horn width >3mm

5. "Mickey mouse" ventricles: Ballooning of frontal horns of lateral ventricles and third ventricle it indicates aqueductal obstruction.

6. Thinned out Corpus Callosum

7. Inferiorly displaced fornix