Head and Cranial Contents
In infants up to about 3 months of age the "flower" method of dissection of the head is preferred; in older children the usual method is the same as that for removing the adult brain.
Flower Method. After external inspection of the scalp, face, and neck as well as photographic documentation of the pathology, a coronal incision is made in the scalp starting behind one ear, cutting posterior to the vertex toward the other ear. The incision permits satisfactory reconstruction of the head should further viewing of the body be required; it also imparts a degree of stability should skull bones be retained for examination. The size of the anterior fontanel and width of suture lines are noted. Where there is increased intracranial pressure, particularly of recent origin, the fontanel is tense and bulging and the suture lines may be wider than normal. If there has been long-standing increased intracranial pressure, the anterior fontanel often extends forwards, widely separating the frontal bones along their entire length.
The anterior fontanel is incised parasagittally with a scalpel, taking care not to damage the sagittal sinus. Incisions are extended forward and backward on each side in turn. On each side, the frontoparietal and parieto-occipital suture lines are incised. The frontal and parietal bone flaps can be deflected laterally (like the opening of flowers, see Fig. 25.5) and the surface of the brain inspected on each side in turn (Prahlow et al. 1998). Observe the cerebral gyral pattern: the normal gyral pattern appears uniform. Its increasing complexity with fetal maturity has been well documented by Dorovini-Zis and Dolman (1977).
Next, the head is tipped forwards and laterally and the occipital pole gently lifted with a finger or scalpel handle to inspect the falx and tentorium for hemorrhage and tears. Congestion and focal hemorrhage within the dural folds are common and usually insignificant. The whole of the falx and tentorium can be examined in this way.
The removal of the brain will usually follow techniques used in adults. Under special circumstances as well as for special documentation, removal under water or separate removal of each of the hemispheres may be recommended. Moreover, special attention is paid to the subdural space. In the presence of sub-dural hematoma (SDH), the disrupted bridging vein must be located - if possible. The bridging veins are attached to the sagittal sinus. Acceleration of the head may lead to stress on these veins which can disrupt and bleed into the subdural space.
After removal, the brain is placed in fixative. After about 14 days, the brain should be examined in detail and described meticulously after external inspection. The mass (and volume) is to be measured, then - depending on the context - the brain is cut in the frontal, transverse or sagittal plane and the findings recorded photographically and by full description. Due to the high water content of the fetal, newborn, and infant brain, the subsequent dehydration process of tissue blocks before routine embedding in paraffin should proceed very slowly, allowing about twice as much time as the dehydration of histological blocks of adult brain tissue.
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