Lateral-type posterior fossa ependymomas in pediatric patients: a national collaborative study.

PURPOSE: To review a multicentric series of lateral-type posterior fossa ependymomas operated in the last ten years and to analyze the factors related to clinical evolution and tumor survival. METHODS: Descriptive, retrospective study. Active members of the Spanish Society of Pediatric Neurosurgery were invited to participate in this multicentric study. Clinical and radiological data were incorporated to an open database. The role of histologic grade, grade of resection, postoperative morbidities, and clinical follow-up was evaluated through bivariate associations (chi-square), Kaplan-Meier's curves (log-rank test), and multivariate analysis (binary logistic regression). RESULTS: Fourteen centers entered the study, and 25 cases with a minimum follow-up of 6 months were included. There were 13 boys and 12 girls with a mean age close to 3 years. Mean tumor volume at diagnosis was over 60 cc. A complete resection was achieved in 8 patients and a near-total resection in 5 cases. Fifteen tumors were diagnosed as ependymoma grade 2 and ten as ependymoma grade 3. Major morbidity occurred postoperatively in 14 patients but was resolved in twelve within 6 months. There were six cases of death and 11 cases of tumor progression along the observation period. Mean follow-up was 44.8 months. Major morbidity was significantly associated with histologic grade but not with the degree of resection. Overall and progression-free survival were significantly associated with complete surgical resection. At the last follow-up, 16 patients carried a normal life, and three displayed a mild restriction according to Lansky's scale. CONCLUSIONS: Lateral-type posterior fossa ependymomas constitute a specific pathologic and clinical tumor subtype with bad prognosis. Gross total resection is the goal of surgical treatment, for it significantly improves prognosis with no additional morbidity. Neurological deficits associated to lower cranial nerve dysfunction are common, but most are transient. Deeper genetic characterization of these tumors may identify risk factors that guide new treatments and stratification of adjuvant therapies.

Direct cortical stimulation with cylindrical depth electrodes in the interhemispheric fissure for leg motor evoked potential monitoring.

OBJECTIVE: To evaluate cylindrical depth electrodes in the interhemispheric fissure as an alternative to subdural strip electrodes for direct cortical stimulation (DCS) leg motor evoked potential (MEP) monitoring. METHODS: A cylindrical depth electrode was positioned in the interhemispheric fissure of 37 patients who underwent supratentorial brain surgery. Leg sensory and motor cortices were localized by highest tibial nerve somatosensory evoked potential amplitude and lowest DCS leg MEP threshold; the lowest-threshold electrode was then used for DCS leg MEP monitoring. RESULTS: Intraoperative leg MEPs were obtained from all the patients in the series. The mean intensity applied for leg MEP monitoring with the cylindrical depth electrode was 15.2 ± 4.0 mA. No complications secondary to neurophysiological monitoring were detected. CONCLUSIONS: Lower extremity MEPs were consistently recorded using a multi-contact cylindrical depth electrode in the interhemispheric fissure by DCS. SIGNIFICANCE: Cylindrical depth electrodes may be a safe and effective alternative for DCS in the interhemispheric fissure, where subdural strips are difficult to place.

Electrical stimulation threshold in chronically compressed lumbar nerve roots: Observational study.

OBJECTIVES: Intraoperative neuromonitoring (IONM) is a common practice in spinal surgery, mostly during pedicle screw placement. However, there is not enough information about the factors that can interfere with IONM data. One of these factors may be existing damage of the nerve root whose function must be preserved. The main purpose of the present study is to evaluate the effect of chronic compression in lumbar nerve roots in terms of stimulation thresholds during direct nerve stimulation. PATIENTS AND METHODS: Direct electrical stimulation was performed in 201 lumbar nerve roots during lumbar spinal procedures under general anaesthesia in 80 patients with different lumbar spinal pathologies. Clinical and radiological data were reviewed in order to establish the presence of chronic compression. RESULTS: Chronically compressed nerve roots showed a higher stimulation threshold than non compressed nerve roots (11.93 mA vs. 4.33 mA). This difference was confirmed with intra-subject comparison (paired sample t test, p=0.012). No other clinical factors were associated with this higher stimulation threshold in lumbar nerve roots. CONCLUSION: A higher stimulation threshold is present in compressed lumbar nerve roots than non compressed roots. This needs to be taken into consideration during pedicle screw placement, where intraoperative neurophysiological monitoring is being used.

Quistes aracnoideos: embriología y anatomía patológica / Arachnoid cysts: Embriology and pathology

Existe en la actualidad todavía mucha controversia en cuanto al origen de los quistes aracnoideos. En el caso de los quistes aracnoideos congénitos, la teoría más aceptada es aquella que explica cómo se forman a partir del desarrollo anómalo de la membrana aracnoidea, la cual se desdobla facilitando la acumulación de líquido cefalorraquídeo en su interior, dando lugar a un quiste. Esta teoría parece explicar el origen de los quistes aracnoideos de convexidad y silvianos, mientras que aquellos en otras localizaciones podrían ser debidos a otras causas. En el estudio anatomopatológico se aprecia que la pared de los quistes aracnoideos difiere poco de la membrana aracnoidea normal, pudiendo estar engrosada debido a un aumento de depósito de material colágeno. Exponemos el desarrollo embriológico normal de la aracnoides, las alteraciones que se producen en dicho desarrollo y que condicionan la formación de los quistes aracnoideos describiendo sus hallazgos anatomopatológicos más característicos

There is still great controversy surrounding the origin of the arachnoid cyst. The most accepted theory in the case of congenital cysts explains how they are formed from an anomalous development of the arachnoid membrane, which is unfolded allowing the accumulation of cerebrospinal fluid inside and creating a cyst. This theory seems to explain the origin of convexity and sylvian cistern arachnoid cysts, whereas those in other locations might be due to other mechanisms. In the anatomopathological analysis, the arachnoid cyst wall can be seen as having few differences from normal, although thickened due to an increase quantity of collagenous material

[Arachnoid cysts: Embriology and pathology]. / Quistes aracnoideos: embriología y anatomía patológica.

There is still great controversy surrounding the origin of the arachnoid cyst. The most accepted theory in the case of congenital cysts explains how they are formed from an anomalous development of the arachnoid membrane, which is unfolded allowing the accumulation of cerebrospinal fluid inside and creating a cyst. This theory seems to explain the origin of convexity and sylvian cistern arachnoid cysts, whereas those in other locations might be due to other mechanisms. In the anatomopathological analysis, the arachnoid cyst wall can be seen as having few differences from normal, although thickened due to an increase quantity of collagenous material. A description of the embryological development of the arachnoid layer and cyst formation is presented, describing the main anatomopathological findings.

Encefalitis antirreceptor de NMDA en una niña de 3 años sin patología tumoral asociada / Anti-NMDA receptor encephalitis in a 3-year-old girl with no associated pathology involving a tumour

Introducción. La encefalitis por anticuerpos contra el receptor de NMDA (N-metil D-aspartato) es una enfermedad relativamente frecuente, aunque infradiagnosticada hasta hace unos años. Cursa de manera predecible y de forma parecida en adultos y en niños, aunque existen ciertas diferencias; su asociación con tumores es menor. Caso clínico. Niña de 3 años que ingresó en nuestro hospital con un cuadro compatible con encefalitis aguda, por lo que se instauró tratamiento con aciclovir. Durante su ingreso alternó períodos de escasa respuesta a estímulos con períodos de agitación y progresó a mutismo completo, a lo que se sumaron problemas de sueño. Comenzó con crisis epilépticas, movimientos distónicos y alteraciones autonómicas. La resonancia magnética craneal mostró una leve atrofia cortical y el electroencefalograma un enlentecimiento generalizado del trazado de base. Las punciones lumbares fueron repetidamente normales desde el punto de vista citológico y bioquímico. Ante la tórpida evolución se inició tratamiento con metilprednisolona y posteriormente con inmunoglobulinas, sin mejoría. Tras confirmarse la positividad de los títulos de anticuerpos antirreceptor de NMDA en el líquido cefalorraquídeo y el suero, se administró ciclofosfamida, con mejoría progresiva de la sintomatología hasta su recuperación completa. Tras 10 meses de seguimiento sin tratamiento, no ha presentado recaídas y se ha descartado la presencia de tumores. Conclusiones. Ante un cuadro de encefalitis, asociado a alteraciones del comportamiento y movimientos anormales, es importante sospechar esta enfermedad, ya que un diagnóstico temprano y la instauración del tratamiento adecuado podrían mejorar su pronóstico (AU)

Introduction. Encephalitis due to NMDA receptors antibodies is a relatively common condition but it was under diagnosed until recently. It courses predictably and similarly in adults and children, although there are some differences, still less its association with tumours. Case report. A 3 years-old girl who was admitted to our hospital with symptoms compatible with acute encephalitis, so we started treatment with acyclovir. During admission she was alterning periods of poor response to stimuli with periods of agitation, and progressed to complete silence, adding sleep problems. She suffered epileptic seizures, dystonic movements and autonomic disturbances. Cranial MRI showed mild cortical atrophy and EEG generalized slowing of base tracing. Repeated samples of cerebral spinal fluid were normal from cytological and biochemical point of view. In view of the torpid evolution she began methylprednisolone therapy and later inmunoglobulins with no improvement. Upon confirmation of the positivity for NMDA receptors antibodies in cerebral spinal fluid and serum, cyclophosphamide was administered, with gradual improvement of symptoms until full recovery. After ten months of follow-up without treatment she has not presented relapses and has ruled out the presence of tumours. Conclusions. It is important to recognize encephalitis with behavioural changes and abnormal movements, because early diagnosis and the beginning of appropriate therapy could improve the prognosis (AU)

Acute hemicerebellitis with obstructive hydrocephalus in a young adult.

BACKGROUND: Acute cerebellitis is a rare entity, described in the pediatric population, usually of viral or autoimmune origin, bilateral and symmetric, and with good prognosis. Only 13 cases of unilateral cerebellitis have been reported thus far. To the best of our knowledge, this is the first case of hemicerebellitis in the literature reported in a young adult that caused acute hydrocephalus requiring surgical treatment. CASE DESCRIPTION: We report an unusual case of an 18-year-old man, without previous infectious symptoms, who developed acute obstructive hydrocephalus secondary to hemicerebellitis. A ventricular drainage was placed. The affected cerebellar hemisphere was later explored and biopsied, and edematous tissue, with an inflammatory reaction of the leptomeninges, was obtained. With corticosteroids and antivirals, the neurologic symptoms disappeared and the MRI evolved to normal in 2 week's time. CONCLUSIONS: Hemicerebellitis must be considered in the differential diagnosis of cerebellar mass lesions, even in young adults. Although rare, clinically significant hydrocephalus may develop. Despite the availability of MRI, a high index of suspicion is still required to accurately diagnose this entity. The histologic substrate seems to be localized meningitis. The edematous reaction of the cerebellar parenchyma supports the usefulness of corticoids in the treatment strategy of this disease.