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  • Author or Editor: Alexandre C. Carpentier x
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Alexandre C. Carpentier, R. Todd Constable, Michael J. Schlosser, Alain de Lotbinière, Joseph M. Piepmeier, Dennis D. Spencer and Issam A. Awad

Object. Functional magnetic resonance (fMR) imaging of the motor cortex is a potentially powerful tool in the preoperative planning of surgical procedures in and around the rolandic region. Little is known about the patterns of fMR imaging activation associated with various pathological lesions in that region or their relation to motor skills before surgical intervention.

Methods. Twenty-two control volunteers and 44 patients whose pathologies included arteriovenous malformations (AVMs; 16 patients), congenital cortical abnormalities (11 patients), and tumors (17 patients) were studied using fMR imaging and a hand motor task paradigm. Activation maps were constructed for each participant, and changes in position or amplitude of the motor activation on the lesion side were compared with the activation pattern obtained in the contralateral hemisphere. A classification scheme of plasticity (Grades 1–6) based on interhemispheric pixel asymmetry and displacement of activation was used to compare maps between patients, and relative to hand motor dexterity and/or weakness.

There was 89.4% interobserver agreement on classification of patterns of fMR imaging activation. Displacement of activation by mass effect was more likely with tumors. Cortical malformations offer a much higher functional reorganization than AVMs or tumors. High-grade plasticity is recruited to compensate for severe motor impairment.

Conclusions. Pattern modification of fMR imaging activation can be systematized in a classification of motor cortex plasticity. This classification has shown good correlation among grading, brain lesions, and motor skills. This proposal of a classification scheme, in addition to facilitating data collection and processing from different institutions, is well suited for comparing risks associated with surgical intervention and patterns of functional recovery in relation to preoperative fMR imaging categorization. Such studies are underway at the authors' institution.

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Christian Sainte-Rose, Giuseppe Cinalli, Franck E. Roux, Wirginia Maixner, Paul D. Chumas, Maheir Mansour, Alexandre Carpentier, Marie Bourgeois, Michel Zerah, Alain Pierre-Kahn and Dominique Renier

The authors conducted a study to evaluate the effectiveness of endoscopically guided third ventriculostomy in the pre- and postoperative management of hydrocephalus in pediatric patients who harbored posterior fossa tumors.

Between October 1, 1993, and December 31, 1997, a total of 206 consecutive children with posterior fossa tumors underwent surgery at Hôpital Necker-Enfants Malades in Paris. Ten patients in whom shunts were implanted at the referring hospital were excluded. The medical records and neuroimaging studies obtained in the remaining 196 patients were reviewed. These patients were categorized into three groups: 67 patients with hydrocephalus on admission in whom endoscopically guided third ventriculostomy was performed prior to tumor removal (Group A); 82 patients with hydrocephalus in whom preliminary third ventriculostomy was not performed and who were managed in a “conventional way” (Group B); and 47 patients without ventricular dilation on admission (Group C).

There was no significant difference between Group A and Group B patients with respect to age at presentation, evidence of metastatic disease, degree of tumor resection, or follow up. In the patients in Group A, however, more severe hydrocephalus was present (p < 0.01). Patients in Group C were, in this respect, different from the other two groups.

Ultimately, only four patients (6%) in Group A as compared with 22 patients (27 %) in Group B (p = 0.001) had progressive hydrocephalus requiring treatment following removal of the posterior fossa tumor. Sixteen patients (20%) in Group B underwent insertion of a ventriculoperitoneal shunt, which is similar to the incidence of this procedure reported in the literature and significantly different from that in Group A (p < 0.016). The other six patients in Group B (6%) were treated by endoscopically guided third ventriculostomy after tumor removal. In Group C, two patients (4%) with postoperative hydrocephalus underwent endoscopically guided third ventriculostomy.

In three of the patients who required placement of cerebrospinal fluid shunts several episodes of shunt malfunction occurred; these were ultimately managed by performing endoscopic third ventriculostomy and definitive removal of the shunt.

There were no cases of death and four cases of transient morbidity associated with the ventriculostomy.

Third ventriculostomy is feasible even in the presence of posterior fossa tumors (including brainstem tumors). When performed prior to posterior fossa surgery, it significantly reduces the incidence of postoperative hydrocephalus. Furthermore, it provides a valid alternative to the placement of permanent shunts in cases in which hydrocephalus develops following posterior fossa surgery, and it may negate the need for the shunt in cases in which the shunt malfunctions.

Although the authors acknowledge that the routine application of third ventriculostomy in selected patients may result in a proportion of patients undergoing an “unnecessary” procedure, they believe that because of patients' less complicated postoperative course, the low morbidity rate, and the high success rate of third ventriculostomy, further investigation of this protocol is warranted.

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Christian Sainte-Rose, Giuseppe Cinalli, Franck E. Roux, Wirginia Maixner, Paul D. Chumas, Maher Mansour, Alexandre Carpentier, Marie Bourgeois, Michel Zerah, Alain Pierre-Kahn and Dominique Renier

Object. The authors undertook a study to evaluate the effectiveness of endoscopic third ventriculostomy in the management of hydrocephalus before and after surgical intervention for posterior fossa tumors in children.

Methods. Between October 1, 1993, and December 31, 1997, a total of 206 consecutive children with posterior fossa tumors underwent surgery at Hôpital Necker—Enfants Malades in Paris. Excluded were 10 patients in whom shunts had been placed at the referring hospital. The medical records and neuroimaging studies of the remaining 196 patients were reviewed and categorized into three groups: Group A, 67 patients with hydrocephalus present on admission in whom endoscopic third ventriculostomy was performed prior to tumor removal; Group B, 82 patients with hydrocephalus who did not undergo preliminary third ventriculostomy but instead received conventional treatment; and Group C, 47 patients in whom no ventricular dilation was present on admission.

There were no significant differences between patients in Group A or B with respect to the following variables: age at presentation, evidence of metastatic disease, extent of tumor resection, or follow-up duration. In patients in Group A, however, more severe hydrocephalus was demonstrated (p < 0.01); the patients in Group C were in this respect different from those in the other two groups.

Ultimately, there were only four patients (6%) in Group A compared with 22 patients (26.8%) in Group B (p = 0.001) in whom progressive hydrocephalus required treatment following removal of the posterior fossa tumor. Sixteen patients (20%) in Group B underwent insertion of a ventriculoperitoneal shunt, which is similar to the incidence reported in the literature and significantly different from that demonstrated in Group A (p < 0.016). The other six patients (7.3%) were treated by endoscopic third ventriculostomy after tumor resection. In Group C, two patients (4.3%) with postoperative hydrocephalus underwent endoscopic third ventriculostomy.

In three patients who required placement of CSF shunts several episodes of shunt malfunction occurred that were ultimately managed by endoscopic third ventriculostomy and definitive removal of the shunt. There were no deaths; however, there were four cases of transient morbidity associated with third ventriculostomy.

Conclusions. Third ventriculostomy is feasible even in the presence of posterior fossa tumors (including brainstem tumors). When performed prior to posterior fossa surgery, it significantly reduces the incidence of postoperative hydrocephalus. The procedure provides a valid alternative to placement of a permanent shunt in cases in which hydrocephalus develops following posterior fossa surgery, and it may negate the need for the shunt in cases in which the shunt malfunctions. Furthermore, in patients in whom CSF has caused spread of the tumor at presentation, third ventriculostomy allows chemotherapy to be undertaken prior to tumor excision by controlling hydrocephalus.

Although the authors acknowledge that the routine application of third ventriculostomy in selected patients results in a proportion of patients undergoing an “unnecessary” procedure, they believe that because patients' postoperative courses are less complicated and because the incidence of morbidity is low and the success rate is high in those patients with severe hydrocephalus that further investigation of this protocol is warranted.