Compensatory Hippocampal Neurogenesis in the Absence of Cognitive Impairment Following Experimental Hippocampectomy in Adult Rats.

Temporal lobe epilepsy (TLE) is the commonest type of focal epilepsy in adult humans, and hippocampal sclerosis (HS) is the main pathological finding in this type of epilepsy. In refractory TLE, patients are indicated for unilateral resection of the affected hippocampus by a surgical procedure called hippocampectomy which generally does not cause any cognitive impairment. Once adult hippocampus is a region of endogenous neurogenesis, even in elderly people, we have hypothesized that a compensatory increase in hippocampal neurogenesis might occur in the remaining hippocampus after unilateral hippocampectomy. To test this hypothesis, we performed unilateral hippocampectomy in adult Wistar rats, which were perfused at 15 (G15) and 30 (G30) days post-surgery. Eighteen Wistar rats were randomly distributed in the following experimental groups: control (no surgery, N = 6), G15 (N = 6), and G30 (N = 6). Adjacent cortex and hippocampus of the left hemisphere were completely removed. Behavioral procedures were performed to address possible cognitive impairments. Brains were collected and fixed from animals belonging to all experimental groups. Gross histopathology was performed using thionine staining. Neuroblasts and mature neurons were immunolabeled using anti-doublecortin (DCX) and anti-NeuN antibodies, respectively. Numbers of DCX and NeuN positive cells were quantified for all experimental groups. Animals submitted to hippocampectomy did not present any cognitive impairment as evaluated by eight-arm radial maze behavioral test. The remaining hippocampus presented a higher number of DCX positive cells compared to control (p < 0.001, ANOVA-Tukey) at both G15 and G30. A higher number of NeuN positive cells were present in the granular layer of dentate gyrus at G30 compared to control and G15 (p < 0.001, ANOVA-Tukey). The data suggest that unilateral hippocampectomy induces compensatory neurogenic effect in the contralateral hippocampus. This may underlie the reported absence of significant cognitive impairment and parallels the findings in human patients submitted to unilateral hippocampectomy to treat refractory TLE.

Endoscopic coagulation of choroid plexus in three children with severely advanced forms of hydrocephalus.

OBJECT: The development of modern neuroendoscopic technology brought back the use of choroid plexus surgery for the treatment of some patients with hydrocephalus. This study explored the use of endoscopic coagulation of the choroid plexus (ECCP) for the treatment of severely advanced forms of hydrocephalus in three children. PATIENTS AND METHODS: Three children with markedly dilated ventricles underwent ECCP. The first child had fetal hydranencephaly, the second had holoprosencephaly, and the third had severe hydrocephalus associated with other congenital malformations. All three children had had previous ventriculoperitoneal (VP) shunts, and ECCP was done because of shunt malfunction. All three children underwent computed tomography and magnetic resonance imaging to confirm the presence and to measure the size of the choroid plexus before surgery. ECCP was performed through a right frontal burr hole. A rigid neuroendoscope and monopolar coagulator were used to achieve choroid plexus coagulation. RESULTS: The first child died 21 days after surgery because of generalized infection originating from the lungs. The second child needed a ventriculoatrial shunt 45 days after ECCP, and the third child needed VP shunt 3 months after ECCP. CONCLUSIONS: ECCP, although not an alternative to ventricular shunt, is a safe procedure and should be tried in some children with severe advanced, low progressive, and hopeless forms of hydrocephalus. Long-term watchful follow-up is mandatory after surgery. When the risk of complications after VP shunting is relatively high in children with severe forms of hydrocephalus, ECCP seems to be worth trying. Delayed timing of VP shunting after ECCP would be meaningful for children with a high risk of shunt complications.

Spinal cord compression secondary to epidural bilharzioma: case report.

A case of an epidural granuloma due to Schistosoma mansoni compressing the spinal cord at T7-T9 is presented. The patient, a 35-year-old Brazilian man, started complaining of recurrent back pain since 2003. A magnetic resonance imaging (MRI) scan showed a large epidural mass extending from T7 to T9 and causing mild spinal cord compression. Through a bilateral laminectomy the bilharzioma was subtotally removed without significant bleeding. The histopathology confirmed the diagnosis of granuloma due to S. mansoni. The patient recovered completely. Although the MRI is nonspecific, this differential diagnosis should be included in homogeneous epidural lesions without bone involvement, more than ever in endemic countries or during the evaluation of travelers to those regions.

The retinal ganglion cell classes of New World primates

In the primate retina there are distinct ganglion cell classes, exhibiting paarticular morphologies and central projections, each responsible for conveying particular types of visual information to the brain. The chief retinal imputs to the cortex arise from specific ganglion cell classes, M-ganglion cells, responsible for carrying the luminance signal, and P-ganglion cells, that convey the red-green color oppnent signal, as well as high contrast luminance signal. There are other ganglion cell classes, such as small-field bistratified cells, exhibiting dentrites that stratify at two different levels in the inner plexiform layer, which convey the blue-yellow color oppnent signal. Most published data concerning primate retinal ganglion cell anatomy and physiology have been obtained from Old World species. Studies on New World monkeys have recently become of interest since they differ from the Old World monkeys with respect to the color vivion inheritance pattern. On reviewing retinal ganglion cell layer organization in New World monkeys, it seems that there are more similarities than differences in relation to the Old Work monkeys. Diurnal genera of New World monkeys exhibit a well-developed fovea centralis and ganglion cell density peak, as well as peripheral density values which are in the range reported for Old World monkeys and human. Moreover, all the major ganglion cell classes identified in Old World monkeys are also present in New World primates. Up to now, no obvious anatomical differences between dechromats and trichromats have been reported. The only genus that is significantly different from the others is the Aotus. It exhibits lower ganglion cell density in the central retina, and apparently lacks the small-field bistratified cells.