Table 7 Systematic trimming of the occipitotemporal region (Block A)

TS-1

0 min

Ventral view of whole brain

Transverse line through centre of pituitary stalk and the broadest laterolateral extension of the piriform lobe

2D knife axis: laterolateral.

Standard transverse section of the diencephalon.

Easy

Plane: transverse.

Exposes the amygdaloid nucleus, thalamus and often lateral geniculate nucleus, piriform cortex.

Blade movement: ventrodorsal.

Allows for localisation of rostral tip of hippocampal tail and head/TVB.

TS-2

2 min

Ventral view of brainstem

Transverse line 2 mm caudal to the rostral border of TFOP

2D knife axis: ventrodorsal.

Standard transverse section of the midbrain.

Easy

Plane: transverse.

Prerequisite for TVB section

Blade movement: laterolateral

TILT-1

4 min

Caudal view of occipital lobe and rostral mesencephalic stump

Horizontal line just dorsal to transverse fibres of the pons

2D knife axis: laterolateral.

Epilepsy-specific sections of TVB.

Easy but requires some practice

Plane: oblique, transverse with rostral inclination so that the blade cuts the caudal temporal lobe flexure at right angle.

Also shows prepiriform cortex, peri/entorhinal cortex.

Blade movement: from caudoventral to rostodorsal.

HOR-1

7 min

Same as before

Horizontal line through the upper mesencephalic aquaeduct

2D knife axis: laterolateral.

Epilepsy-specific section.

Easy

Plane: horizontal.

Exposes CV of both hippocampi, parahippocampal gyri, postrhinal and caudal perirhinal cortex as well as lateral geniculate nucleus.

Blade movement: caudorostral.

TILT-2L/R

9 min

Same as previous two steps

Lines perpendicularly set through the vertex of both occipitotemporal flexures.

2D knife axis:

Epilepsy-specific sections of both hippocampal OV and associated parahippocampal gyri, rostral colliculi, optic radiations and main visual cortices.

Easy but requires some practice

2R: dextroventral to sinistrodorsal.

2L: sinistroventral to dextrodorsal

Plane: oblique, longitudinal, with lateral inclination (45° and 135°).

Also, standard procedure in transtentorial herniation.

Blade movement: caudorostral.

TS-3

11 min

Lateral view of dorsal wedge remaining from tissue Block A

Transverse line just 1–2 mm caudal to the level of the dorsomedial tip of hippocampus.

2D knife axis: laterolateral.

Epilepsy-specific section of dorsomedial hippocampal tail and hippocampal commissure, corpus callosum, occipitomesial cortex including cingulate gyrus and associated subcortical white matter.

Moderately difficult as the rostrocaudal range is very small

Plane: transverse.

Blade movement: dextrodorsal to sinistroventral or vice versa.