Duplication of 7q34 is specific to juvenile pilocytic astrocytomas and a hallmark of cerebellar and optic pathway tumours.

BACKGROUND: Juvenile pilocytic astrocytomas (JPA), a subgroup of low-grade astrocytomas (LGA), are common, heterogeneous and poorly understood subset of brain tumours in children. Chromosomal 7q34 duplication leading to fusion genes formed between KIAA1549 and BRAF and subsequent constitutive activation of BRAF was recently identified in a proportion of LGA, and may be involved in their pathogenesis. Our aim was to investigate additional chromosomal unbalances in LGA and whether incidence of 7q34 duplication is associated with tumour type or location. METHODS AND RESULTS: Using Illumina-Human-Hap300-Duo and 610-Quad high-resolution-SNP-based arrays and quantitative PCR on genes of interest, we investigated 84 paediatric LGA. We demonstrate that 7q34 duplication is specific to sporadic JPA (35 of 53 - 66%) and does not occur in other LGA subtypes (0 of 27) or NF1-associated-JPA (0 of 4). We also establish that it is site specific as it occurs in the majority of cerebellar JPA (24 of 30 - 80%) followed by brainstem, hypothalamic/optic pathway JPA (10 of 16 - 62.5%) and is rare in hemispheric JPA (1 of 7 - 14%). The MAP-kinase pathway, assessed through ERK phosphorylation, was active in all tumours regardless of 7q34 duplication. Gain of function studies performed on hTERT-immortalised astrocytes show that overexpression of wild-type BRAF does not increase cell proliferation or baseline MAPK signalling even if it sensitises cells to EGFR stimulation. CONCLUSIONS AND INTERPRETATION: Our results suggest that variants of JPA might arise from a unique site-restricted progenitor cell where 7q34 duplication, a hallmark of this tumour-type in association to MAPK-kinase pathway activation, potentially plays a site-specific role in their pathogenesis. Importantly, gain of function abnormalities in components of MAP-Kinase signalling are potentially present in all JPA making this tumour amenable to therapeutic targeting of this pathway.

[Pain and amyotrophy in upper members in a cirrhotic patient with Pott's disease]. / Dolor y amiotrofia en miembros superiores en una paciente cirrótica afecta del mal de Pott.

We report the case of a 56 year old cirrhotic woman who presented during the course of a tuberculous spondylodiscitis affecting T9-T10, a clinical picture consistent with neuralgic amyotrophy affecting the right shoulder first, and later also the left one (Parsonage-Turner syndrome). This is an uncommonly diagnosed entity of unknown etiology and pathogenesis. Magnetic resonance images (MRI) include high signal intensity in supra and infraspinatus muscles and other muscles of the shoulder girdle, compatible with muscle oedema associated with denervation. These features, combined with the ability of MRI to exclude local problems as tendinitis stresses the importance of this technique in the diagnostic evaluation of patients with neuralgic amyotrophy.

Brainstem Gliomas. A 10-year institutional review.

Case records of 37 patients with a diagnosis of brainstem glioma treated at the Montreal Children's Hospital from June 1989 to June 1999 were reviewed. 15 patients had diffuse pontine gliomas and 22 patients had focal forms of brainstem gliomas. The two groups were compared with respect to age, clinical evolution, radiological appearance, type of surgery practised, histological diagnosis, adjuvant treatments and survival. A non-pontine brainstem location, a cystic or exophytic component, bright enhancement with gadolinium injection, a histological diagnosis of pilocytic astrocytoma or ganglioglioma were favourable prognostic factors. Progression-free survival and overall survival were significantly worse in the group of patients with diffuse pontine gliomas. The relative impact of radical surgery and/or radiotherapy is analysed. Surgery coupled to adjuncts such as navigation, ultrasound and monitoring plays an important role for focal brainstem lesions. Focal/conformal radiotherapy has an adjuvant role but better treatments are needed for the diffuse pontine brainstem lesions.

Intractable epilepsy after a functional hemispherectomy: important lessons from an unusual case. Case report.

Residual seizures after functional hemispherectomy occur in approximately 20% of patients with catastrophic epilepsy. These episodes are traditionally attributed to incomplete disconnection, persistent epileptogenic activity in the ipsilateral insular cortex, or bilateral independent epileptogenic activity. The authors report on the case of an 8-year-old boy with an intractable seizure disorder who had classic frontal adversive seizures related to extensive unilateral left hemispheric cortical dysplasia. The initial intervention consisted of extensive removal of the epileptic frontal and precentral dysplastic tissue and multiple subpial transections of the dysplastic motor strip, guided by intraoperative electrocorticography, Subsequently, functional hemispherectomy including insular cortex resection was performed for persistent attacks. After a seizure-free period of 6 months, a new pattern ensued, consisting of an aura of fear, dystonic posturing of the right arm, and unusual postictal hyperphagia coupled with an interictal diencephalic-like syndrome. Electroencephalography and ictal/interictal single-photon emission computerized tomography were used to localize the residual epileptic discharges to deep ipsilateral structures. Results of magnetic resonance imaging indicated a complete disconnection except for a strip of residual frontobasal tissue. Therefore, a volumetric resection of the epileptogenic frontal basal tissue up to the anterior commissure was completed. The child has remained free of seizures during 21 months of follow-up review. Standard hemispherectomy methods provide extensive disconnection, despite the presence of residual frontal basal cortex. However, rarely, and especially if it is dysplastic, this tissue can represent a focus for refractory seizures. This is an important consideration in determining the source of ongoing seizures posthemispherectomy in patients with extensive cortical dysplasia. It remains important to assess them fully before considering their disease refractory to surgical treatment.

Effectiveness of a head injury program for children: a preliminary investigation.

OBJECTIVE: The purpose of this study was to investigate whether a more coordinated, comprehensive head injury rehabilitation program provided at a children's trauma center yielded better outcomes than a less coordinated, less comprehensive program. DESIGN: Using a quasi-experimental design, 64 children with head injury admitted to the center and who received rehabilitation services in either 1995 or 1993 were evaluated by using the Functional Independence Measure for children (WeeFIM)/The Functional Independence Measure (FIM) (e.g., primary outcome measure). Secondary outcomes included "psychosocial adjustment," "return to regular school," and "current problems related to the head injury." RESULTS: No statistically significant differences were found between the groups with respect to mean WeeFIM/FIM scores after controlling for age and injury severity. The 1993 group had poorer scores on the withdrawal subscale of the psychosocial measure (P = 0.02), yet a smaller proportion of these children were enrolled in a special education class (P = 0.02). CONCLUSIONS: This study serves as a model for a larger, definitive study of the effectiveness of rehabilitation for children with head injury. The trends suggest that more comprehensive care may lead to better outcomes.

Dysgenetic mesial temporal sclerosis: an unrecognized entity.

Mesial temporal sclerosis (MTS) is the most frequently encountered lesion in adult patients with intractable temporal epilepsy; it is found in isolation in approximately two-thirds of surgically treated cases. Whereas the exact etiology of MTS is still controversial, several reports suggest that this pathologic lesion is both the cause and the consequence of chronic seizures and develops progressively during childhood secondary to recurrent seizures. In order to evaluate the clinical importance of MTS in children, we retrospectively reviewed the clinical charts of children who underwent surgery for medically intractable temporal epilepsy and report cases presenting an amygdalo-hippocampic dual pathology. Six children aged 1.5-16 years (mean +/- SD: 7.5 +/- 3 years) presenting with partial complex seizures (5 cases) or extension spasms (1 case), with onset from 6 months to the age of 8.5 years (mean seizure onset +/- SD: 3 +/- 5 years) underwent anterior temporal lobectomy including resection of the amygdala and hippocampus. All patients exhibited variable degrees of severity of neuronal loss and gliosis in the amygdala and/or hippocampus. The pathological picture of MTS was not isolated, however. Careful pathological examination has thus shown foci of amygdalo-hippocampic neuronal dysplasia in six patients, with concomitant bilaminated fascia dentata in two cases. Postoperatively, no mortality or morbidity was encountered. After a mean follow-up of 2.5 years, four patients are seizure free. One patient had a 80% rate of improvement in seizure frequency, though still having occasional febrile convulsions. In another patient, complex partial seizures resolved, but rare episodes of absence were still observed. These data are in keeping with the hypothesis that MTS could be secondary to repeated seizures. The analysis of this series of patients could suggest that mesiotemporal dysplastic lesions within the amygdalo-hippocampic structures induce seizures, which, in turn, will favor the development of MTS during childhood. MTS could then lead to synaptic reorganization, which can express abnormal hyperexcitability and result in more recurrent seizures. In this way a vicious circle is set up, which may explain the progression of seizures in some patients.

[Hypothalamic hamartoma: detailed presentation of a case]. / Hamartome hypothalamique: présentation détaillée d'un cas.

We describe a seven year old child with a hypothalamic hamartoma. Classical symptoms of hypothalamic hamartoma include gelastic epileptic laughter, precocious puberty, aggressiveness, and progressively worsening epilepsy. After a normal first few years of life, this case presents all these symptoms except the precocious puberty. He has a markedly morbid personality disorder: he assaults strangers and relatives, bites people, spits in their faces unpredictably, is coprolalic and coprophagic, has gelastic laughter, puts pencils, erasers, and other non-comestible objects in his mouth, chews and ingests them, has tics (plays noisily with his saliva, empty chewing, compulsive spitting) and is self-injurious. None of the medications attempted to date have been of any help. Medical prognosis is somber, and this case is difficult to institutionalize, the more "congenial" institutions being insufficiently equipped to protect him and the beneficiaries and staff from his aggressive behavior. MRI showed the typical profile of hypothalamic hamartoma, and the diagnosis was confirmed with partial resection. This case illustrates that a tiny lesion, the size of a small cherry, can have extremely morbid psychological consequences. Detailed neuropsychological evaluation, certain unusual electroencephalographic traits and neurosurgical issues are discussed.

Using the measure of processes of care with parents of children hospitalized for head injury.

Despite recommendations that rehabilitation programs adopt family/patient satisfaction as an outcome measure, few studies have addressed satisfaction with services for children with head injury. This report describes our use of the Measure of Processes of Care (MPOC) to document the perceptions of care of parents whose children were hospitalized with a head injury and to compare parental perceptions of care with those of the service providers (n = 16). The MPOC is a self-administered questionnaire consisting of 56 items, each of which is included in one of five care-giving scales: (1) enabling and partnership; (2) providing general information; (3) providing specific information about the child; (4) coordinated and comprehensive care; (5) respectful and supportive care. The MPOC was mailed to parents of children with a head injury who were consecutively admitted to a pediatric trauma center during a 5-mo period. The results, based on the responses of 73 parents (response rate, 59.3%), revealed that the needs of these parents are being met to varying degrees. Mean scores for the five scales ranged from 4.6 to 6.4 and from 5.9 to 6.6 for parents and providers, respectively. Significant differences between the groups were found for two scales: providing general and specific information. Because of the low percentage of valid responses for three of the five scales, the MPOC appears to be an inappropriate tool for use with parents of children with mild head injury (89%) in the acute care setting. The MPOC, however, is applicable for parents of children who are more severely injured (e.g., average hospital stay, 9 days) and is informative for rehabilitation service providers.

Magnetic resonance imaging in children with voiding dysfunction: is it indicated?

PURPOSE: We evaluated the role of magnetic resonance imaging (MRI) of the lumbosacral spinal cord in children with complicated voiding dysfunction and normal neuro-orthopedic examination. MATERIALS AND METHODS: We reviewed the records of 32 consecutive children with complicated enuresis who were referred for neurosurgical evaluation, including those with a history of refractory voiding dysfunction or incontinence associated with persistent vesicoureteral reflux, encopresis, or associated leg or back pain. Nine patients were excluded from study because of urethral or anorectal anomalies, or failure to meet the inclusion criteria. Eligible for study inclusion were 23 children with a mean age of 8.9 years. Complete neurological and orthopedic examinations were normal in all patients except 1 with mild scoliosis and 1 with congenital facial palsy. RESULTS: Urodynamic studies revealed instability in 14 cases, hypertonia in 7, hyporeflexia in 2 and detrusor-sphincter dyssynergia in 4. Skeletal abnormalities, mostly spina bifida occulta, were detected in 16 of the 23 children (70%). Spinal MRI was normal in 21 patients (91.3%), including 1 with a tethered cord and lipoma associated with a complex skeletal abnormality, and 1 with a nonprogressive, nonsurgical T7 to T9 syrinx. Only the case of lipoma required neurosurgical intervention. CONCLUSIONS: The value of MRI is limited in children with voiding dysfunction and a normal neuro-orthopedic assessment. This study should be reserved for patients with associated neuroorthopedic findings or complex skeletal deformity on plain x-ray.

Continuous unilateral epileptiform discharge and language delay: effect of functional hemispherectomy on language acquisition.

PURPOSE: To assess the efficacy of functional hemispherectomy in promoting language acquisition in a child with severe language delay and continuous left hemispheric epileptiform discharge in the absence of clinical seizures. We report a 6-month-old girl who initially presented with a right hemiparesis secondary to a lesion of probable prenatal origin in the distribution of the left middle cerebral artery. Weeks later, she developed infantile spasms. At 1.5 years of age, because of intractable seizures, the patient had fenestration of the left porencephalic cyst and anterior temporal lobectomy. The seizures ceased; however, language development remained limited to 35 words at 3.5 years of age. The EEG showed almost continuous epileptiform activity over the left hemisphere with no independent epileptiform potentials contralaterally. She underwent a functional left hemispherectomy. METHODS: Imaging, electroencephalographic investigation, pre- and postoperative psychological and speech assessment were carried out. RESULTS: Considerable language, speech, and behavior improvement was noted within 2 months of surgery. CONCLUSIONS: Interictal epileptiform discharges can interfere with the development of contralateral hemispheric function in the absence of clinical seizures. Early functional hemispherectomy may have a role in promoting optimal language development in appropriately selected patients. Although the primary indication for functional hemispherectomy is to control intractable seizures, a secondary proposed indication is to reduce functional impairment of the other hemisphere by electrical interference.

Cerebral arterial ectasia and tuberous sclerosis: case report.

OBJECTIVE AND IMPORTANCE: Tuberous sclerosis is associated with a wide variety of central nervous system abnormalities. Cerebrovascular anomalies are extremely rare, but a case of cerebral arterial ectasia and giant fusiform aneurysm formation in a young child is reported. CLINICAL PRESENTATION: A 5-month-old male patient with tuberous sclerosis presented with seizures, a subependymal tumor, and intraventricular hemorrhage. Cerebral angiography demonstrated a large fusiform aneurysm of the left cavernous internal carotid artery as well as arterial ectasia of the proximal left anterior cerebral and middle cerebral arteries. The patient developed hydrocephalus and died of infectious complications after repeated shunt procedures. CONCLUSION: Tuberous sclerosis is commonly associated with central nervous system lesions. Although rare, cerebrovascular anomalies and aneurysms should be considered in the differential diagnosis of mass lesions to avoid an ill-advised biopsy of a vascular lesion, which could have disastrous consequences.

Use of the prone position in the MRI evaluation of spinal cord retethering.

In order to determine the impact of magnetic resonance imaging (MRI) in the management of spinal cord retethering, we retrospectively reviewed case and imaging records of 51 patients who underwent MRI examination in supine and prone positions. Group 1 included 8 control patients without cord tethering. They exhibited a normal level of the conus medullaris with normal surrounding subarachnoid space, and consistent anterior migration of the conus within the dural sac on MRI in prone position. Group 2 included 17 patients with tethered cord secondary to occult spinal dysraphism (spinal cord lipoma in 6 patients, thick filum terminale in 4, diastematomyelia in 4, myelomeningocele manqué in 2, and dermoid tumour in 1). Supine and prone MRI performed at a median period of time of 6 months after untethering showed resolution of posterior tethering in 5 out of the 7 patients who exhibited pre-operatively dorsal attachment of the spinal cord to the dura. Anterior migration of the conus or of the cord/filum complex in prone position was observed in only 24% of the cases. Group 3 included 26 patients with secondary tethered cord following prior myelomeningocele closure. Their MRI performed at a median interval of time of 11 months following untethering demonstrated resolution of the posterior cord tethering in only 8 out of the 24 patients who exhibited this feature pre-operatively. Anterior migration within the expanded dural sac was never noted in this group. We conclude that spine MRI is of limited value and that prone-positioned MRI is of no additional use in the evaluation of spinal cord retethering.

Impact of urodynamic studies on the surgical management of spinal cord tethering.

To determine the usefulness of urodynamic studies in the management of children with a suspected tethered spinal cord, the authors retrospectively reviewed case records of 25 patients evaluated both pre- and postoperatively using this diagnostic adjunct. All patients were also evaluated with magnetic resonance imaging or computerized tomography myelography. Seven patients who presented initially with orthopedic deformity, skin stigmata, and neurological problems underwent primary cord untethering (Group 1). All seven patients were urologically asymptomatic; all but one had normal findings on urodynamic study. Eighteen patients with prior myelomeningocele closure underwent secondary untethering (Group 2). They presented with urological (11 cases), neurological (three cases), or both urological and neurological (four cases) deterioration. All patients underwent surgery via a microsurgical technique. At a mean follow-up time of 2 years, the only Group 1 patient with preoperative abnormal urodynamic findings normalized following untethering, whereas another asymptomatic patient showed worsened results on his postoperative study. In Group 2, all seven patients with preoperative neurological deterioration improved. Ten of the 15 patients who had isolated or associated preoperative clinical urological deterioration improved or stabilized, whereas five displayed continued deterioration in their bladder function. With respect to urodynamic studies, there was a significant increase in total and pressure-specific bladder capacities following untethering. We conclude that urodynamic studies are useful both diagnostically and in follow-up examinations of patients with tethered cord, that disturbances identified by these studies often precede clinical manifestations of deterioration, and that spinal cord untethering favorably influences the urological status in most patients.

Encephaloduroarterio-synangiosis in a child with sickle cell anemia and moyamoya disease.

We report a black girl with sickle cell anemia. On prophylactic exchange transfusion protocol, she experienced cerebrovascular accidents at 3 and 3.5 years of age, both associated with transient right hemiparesis. At 7.5 years of age, she presented with a partial motor seizure and a left hemiparesis. A cerebral angiogram demonstrated stenosis at the origins of both middle and anterior cerebral arteries bilaterally with extensive basal collateralization. She underwent uncomplicated bilateral encephaloduroarteriosynangiosis (EDAS) procedures using both superficial temporal arteries. At age 9 years, the patient presented with a severe headache and tunnel vision secondary to a stenosis of both posterior cerebral arteries. She underwent bilateral EDAS procedures using both occipital arteries. No complication was encountered. Postoperative cerebral angiogram demonstrated impressive neovascularity at the sites of all four EDAS procedures. Different treatment options of moyamoya disease are discussed.

Cauda equina histiocytosis X.

A young child was admitted with a cauda equina syndrome believed to be progressive, but unrelated to a congenital anomaly. Magnetic resonance imaging studies revealed the presence of an intradural tumor in the cauda equina. A yellow pasty tumor with nerve root infiltration was identified at surgery. Histologic features were pathognomonic for histiocytosis X. The patient's management and review of the literature are discussed.

Comparison of syringopleural and syringosubarachnoid shunting in the treatment of syringomyelia in children.

Case records from the Montreal Children's Hospital containing the diagnosis of shunted syringomyelia were retrospectively reviewed. From 1984 to 1994, 31 patients had their syrinx treated by either syringopleural (19 cases, Group A) or syringosubarachnoid (13 cases, Group B) shunting. One patient was included in both groups. Associated diagnoses included: in Group A, two cases of Chiari I and 14 of Chiari II malformations, 14 cases of shunted hydrocephalus, 13 cases of spina bifida aperta, and three cases of spina bifida occulta; Group B, four cases of Chiari I and two of Chiari II malformations, four cases of shunted hydrocephalus, two cases of spina bifida aperta, and five cases of spina bifida occulta. Eight Group A and six Group B patients had undergone prior posterior fossa decompression. Motor deficits predominated in both groups and arachnoiditis was a uniform operative finding. Neurological follow-up examinations showed 11 Group A patients improved and eight stabilized, whereas on magnetic resonance imaging, 12 cavities appeared to have collapsed, five were markedly reduced, and one had increased. One patient underwent reoperation for pleural effusions and one for shunt displacement. In Group B, one patient improved, eight stabilized, three worsened neurologically, and one was lost to follow-up review. Radiologically, one cavity appeared to have collapsed, six were significantly reduced, two were unchanged, and three had enlarged. The authors conclude that syringopleural shunting is a valuable option for controlling syringomyelia in patients without Chiari malformation or in patients who have previously undergone a craniovertebral decompression or are otherwise asymptomatic from their Chiari malformation.

Radionuclide shuntogram: adjunct to manage hydrocephalic patients.

UNLABELLED: We reviewed our experience with shuntograms to establish technical criteria that would optimize the reliability of this test in managing patients with shunt malfunction. METHODS: Fifty-six shuntograms were performed in 47 children presenting with symptoms of shunt malfunction not elucidated by conventional radiological examination. Shuntograms were performed by injecting 0.5 ml 99mTc-DTPA in the reservoir of the shunt. RESULTS: There were 22 shuntograms in which ventricular reflux occurred and the entire shunt system was visualized. At surgery, three patients in this group presented partial obstruction of the ventricular and/or peritoneal catheter. A second group of patients had 15 shuntograms that showed normal proximal reflux but abnormal distal drainage. Ten patients in this group presented distal obstruction or fracture, valve dysfunction or peritoneal adhesions at surgery. A third group of patients with 19 shuntograms exhibited no proximal reflux. At surgery, twelve had an obstructed ventricular catheter and the last case showed overdrainage. Symptoms of nonsurgical patients abated spontaneously. CONCLUSION: The shuntogram is a useful procedure in the management of patients presenting with shunt-related problems. For consideration as a normal result, a shuntogram must exhibit ventricular reflux, the shunt system must be entirely visualized and the isotope must diffuse uniformly in the peritoneal cavity. Whereas rapid radionuclide clearance is a useful parameter in eliminating a distal obstruction. It is a misleading sign for proximal blockage. Absence of ventricular reflux is highly suggestive of proximal reflux. Implicit to this conclusion is the fact that the presence of a reservoir proximal to the valve greatly facilitates the performance and interpretation of a shuntogram.

"Pseudo-BECRS": intracranial focal lesions suggestive of a primary partial epilepsy syndrome.

Benign epilepsy of childhood with rolandic spikes (BECRS) is an electroclinical entity that is the most common primary partial epilepsy syndrome of childhood. Typically presenting between the ages of 3 and 13 years, it is characterized by a well-recognized seizure pattern arising in a normal child with EEG findings restricted to rolandic/centrotemporal regions. Seizure control is usually easily achieved and prognosis is believed to be uniformly good. Some authors have suggested that individuals fitting the electroclinical parameters of this entity need not undergo neuroimaging due to the benign evolution of this disorder. Five patients presenting over a 13-year period with peribuccal seizures, normal neurologic examinations, and EEG data initially suggestive of BECRS found to have focal lesions on neuroimaging are summarized. Independent bilateral centrotemporal epileptiform abnormalities were seen in 3 patients. Imaging studies (CT, MRI, or both) documented a mass lesion in all in variable locations. Histologic examination documented a low-grade astrocytoma in 3 patients and a cavernous angioma in another. The fifth patient refused treatment or biopsy. Careful retrospective review of the clinical features of these patients reveals variable atypical features in each. Therefore, despite an electroclinical phenotype initially suggestive of the BECRS presentation, the presence of atypical clinical features raises the possibility of an underlying structural lesion and thus a negative neuroimaging study may in some patients be essential to the definitive accurate diagnosis of BECRS.

Supratentorial ectopic ependymoma.

BACKGROUND: Ependymomas usually arise from the ventricular surface. METHODS: We report an 11-year-old female who presented with a supratentorial ectopic ependymoma. RESULTS: The patient presented with a two-month-history of progressive headache, nausea and vomiting. Examination revealed papilledema, horizontal nystagmus, diplopia on upward gaze, and right pronator drift. CT scan showed an enhancing left precentral subcortical lesion measuring 3 cm in diameter with associated edema and mass effect. Its medial border was located 3 cm from the ependymal surface of the ventricle. A firm tumour was dissected from the centrum semiovale white matter, and removed in toto as confirmed on MRI. Pathological examination revealed histological, immuno-histochemical and electron microscopic features consistent with an ependymoma. Spine MRI and bone marrow aspirate, as well as lumbar puncture of cytology failed to show any dissemination. CONCLUSION: From the literature review, this represents an exceptional ependymoma located at the distance from the ventricular system or cisterns. Different pathogenic alternatives are discussed.

Negative-pressure hydrocephalus.

Two cases of children with closed myelodysplasia, Arnold-Chiari malformation, and shunted hydrocephalus who underwent spinal arachnoid cystopleural shunting are presented. Postoperatively, both patients developed craniovertebral symptomatology accompanied by radiologically documented ventricular dilation in spite of negative intracranial pressure and functional ventriculoperitoneal (VP) shunts. Both patients recovered after the cystopleural shunts were revised to increase the resistance to flow within the system. The authors believe that some communication between the arachnoid cyst and the subarachnoid space existed in both cases and that the negative pleural pressure was transmitted preferentially to the spinal and cerebral convexity subarachnoid spaces with relative sparing of the ventricular system. A transmantle pressure gradient was thereby established, leading to ventricular dilation. The authors further suggest that a craniospinal gradient was possibly established as well, leading to craniovertebral symptomatology in the patients. Return of flow in the VP shunts was obtained by correcting this iatrogenic transmantle pressure gradient.