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The aim is to prospectively assess early neurocognitive outcome of children who developed cerebellar mutism syndrome (CMS) following surgical resection of a posterior fossa embryonal tumor, compared with carefully matched control patients. Children who were enrolled on an ongoing IRB-approved protocol for treatment of embryonal tumors, were diagnosed with postoperative CMS, and had completed prospectively planned neuropsychological evaluation at 12 months postdiagnosis were considered eligible. The cognitive outcomes of these patients were examined in comparison to patients without CMS from the same treatment protocol and matched with regard to primary diagnosis, age at diagnosis, and risk/corresponding treatment (n = 22 pairs). Seventeen were also matched according to gender, and 14 were also matched according to race. High-risk patients received 36–39.6 Gy CSI and 3D conformal boost to the primary site to 55.8–59.4 Gy. Average-risk patients received 23.4 Gy CSI and 3D conformal boost to the primary site to 55.8 Gy. Significant group differences were found on multiple cognitive outcomes. While the matched control patients exhibited performance in the average range, patients who developed CMS postsurgery were found to have significantly lower performance in processing speed, attention, working memory, executive processes, cognitive efficiency, reading, spelling, and math. Patients treated for medulloblastoma who experience postoperative CMS show an increased risk for neurocognitive impairment, evident as early as 12 months following diagnosis. This study highlights the need for careful follow-up with neuropsychological evaluation and for obtaining critical support for patients and their families.

OBJECTIVE—"Cerebellar mutis" and subsequent dysarthria (MSD) is a documented complication of posterior fossa surgery in children. In this prospective study the following risk factors for MSD were assessed: type, size and site of the tumour; hydrocephalus at presentation and after surgery, cerebellar incision site, postoperative infection, and cerebellar swelling.
METHODS—In a consecutive series of 42 children with a cerebellar tumour, speech and neuroradiological studies (CT and MRI) were systematically analysed preoperatively and postoperatively. Speech was assessed using the Mayo Clinic lists and the severity of dysarthria using the Michigan rating scale.
RESULTS—Twelve children (29%) developed MSD postoperatively. The type of tumour, midline localisation, and vermal incision were significant single independent risk factors. In addition, an interdependency of possible risk factors (tumour>5 cm, medulloblastoma) was found.
CONCLUSION—MSD often occurs after paediatric cerebellar tumour removal and is most likely after removal of a medulloblastoma with a maximum lesion diameter>5 cm.



Cerebellar mutism is a rare finding associated with resection of posterior fossa tumors or cerebellar hemorrhages. We reviewed the medical records of six children, aged 6 to 12 years, who developed cerebellar mutism after resection of a posterior fossa mass or as a result of posterior fossa trauma. From 1989 to 1994, 210 children underwent posterior fossa resection at our institution, and four developed mutism (an incidence of 1.6%). All four patients had primitive neuroectodermal tumors. The fifth patient experienced trauma, and another patient had an arteriovenous malformation (AVM). In four children, hydrocephalus developed as a result of their tumor or AVM. Four developed cerebellar mutism 24 to 48 hours after surgery or trauma, and one developed cerebellar mutism 5 days after surgery, coincident with hydrocephalus. In one, mutism occurred after a second resection was performed for a recurrence of his posterior fossa tumor. Cerebellar mutism lasted 10 days in one patient and 2 to 8 weeks in the other four. Dysarthria was apparent in four patients during the recovery phase. We suggest trauma to the dentate nucleus and/or its outflow tract, the superior cerebellar peduncle, as a cause of reversible mutism. Because posterior fossa tumors are common in children, mutism should be recognized as an important side effect of surgery.

Objective

The definition of empty sella syndrome is 'an anatomical entity in which the pituitary fossa is partially or completely filled with cerebrospinal fluid, while the pituitary gland is compressed against the posterior rim of the fossa'. Reports of this entities relating to the brain tumors not situated in the pituitary fossa, have rarely been reported.

Methods

In order to analyze the incidence and relationship of empty sella in patients having brain tumors, the authors reviewed preoperative magnetic resonance imaging (MRI) of 72 patients with brain tumor regardless of pathology except the pituitary tumors. The patients were operated in single institute by one surgeon. There were 25 males and 47 females and mean patient age was 53 years old (range from 5 years to 84 years). Tumor volume was ranged from 2 cc to 238 cc.

Results

The overall incidence of empty sella was positive in 57/72 cases (79.2%). Sorted by the pathology, empty sella was highest in meningioma (88.9%, p = 0.042). The empty sella was correlated with patient's increasing age (p = 0.003) and increasing tumor volume (p = 0.016).

Conclusion

Careful review of brain MRI with periodic follow up is necessary for the detection of secondary empty sella in patients with brain tumors. In patients with confirmed empty sella, follow up is mandatory for the management of hypopituitarism, cerebrospinal fluid (CSF) rhinorrhea, visual disturbance and increased intracranial pressure.

Background and Purpose

Posterior fossa syndrome (PFS) occurs in approximately 25% of pediatric patients receiving surgery for midline posterior fossa tumors. Increasing evidence suggests that PFS represents a complex supratentorial cortical dysfunction related to surgery-induced disruption of critical cerebello-cerebral connections. The purpose of this study was to determine whether or not a consistent surgical damage pattern may be identified in PFS patients by early post-operative anatomical imaging analysis of the proximal efferent cerebellar pathway (pECP) and to test whether or not dynamic susceptibility-weighted contrast-enhanced perfusion MRI (DSC) can detect corresponding changes in cerebral cortical perfusion to indicate a secondary, remote functional disturbance which could suggest a diaschisis-like pathomechanism.

Materials and Methods

Eleven patients with post-operative PFS were evaluated retrospectively and paired with age-gender matched controls that did not develop PFS. MRI work-up included DSC within 3-4 weeks post surgery as well as early post-operative anatomical imaging to evaluate components of the pECP.

Results

DSC showed significant decreases in cerebral blood flow (CBF) within frontal regions (p<0.05) and a trend to global cerebral cortical hypoperfusion in patients with PFS. Logistic regression analysis suggested a strong (potentially predictive) relationship between bilateral damage to pECP and the development of PFS (p=0.04).

Conclusion

Our data suggest that the primary cause of PFS is the bilateral surgical damage to the pECP. This leads to a trans-synaptic cerebral cortical dysfunction (a form of bilateral crossed cerebello-cerebral diaschisis), which manifests with DSC-detectable global, but dominantly frontal, cortical hypoperfusion in PFS patients when compared with age-sex matched controls.

Objective. The aim of this study was to determine the posterior cranial fossa volume, cerebellar volume, and herniated tonsillar volume in patients with chiari type I malformation and control subjects using stereological methods. Material and Methods. These volumes were estimated retrospectively using the Cavalieri principle as a point-counting technique. We used magnetic resonance images taken from 25 control subjects and 30 patients with chiari type I malformation. Results. The posterior cranial fossa volume in patients with chiari type I malformation was significantly smaller than the volume in the control subjects (P < 0.05). In the chiari type I malformation group, the cerebellar volume was smaller than the control group, but this difference was not statistically significant (P > 0.05). In the chiari type I malformation group, the ratio of cerebellar volume to posterior cranial fossa volume was higher than in the control group. We also found a positive correlation between the posterior cranial fossa volume and cerebellar volume for each of the groups (r = 0.865, P < 0.001). The mean (±SD) herniated tonsillar volume and length were 0.89 ± 0.50 cm3 and 9.63 ± 3.37 mm in the chiari type I malformation group, respectively. Conclusion. This study has shown that posterior cranial fossa and cerebellum volumes can be measured by stereological methods, and the ratio of these measurements can contribute to the evaluation of chiari type I malformation cases.

Brain tumours form the most common type of solid tumour in children and more that 50% of these are infratentorial. Cerebellar astrocytomas and brain stem gliomas are the commonest posterior fossa glial tumours in children. Cerebellar astrocytomas represent up to 10% of all primary brain tumours and up to 25% of posterior fossa tumors in children, with Low grade gliomas forming the commonest of the cerebellar gliomas. They commonly present with symptoms and signs of raised intracranial pressure due to obstructive hydrocephalus. Radiologically they may be solid or cystic with or without a mural nodule. Surgical excision is the mainstay of treatment and forms the most consistent factor influencing progression free and long term survival. While majority of the tumours are pilocytic astrocytomas, they may also be fibrillary astrocytomas or even high grade tumours. Tumour histology does not appear to be an independent factor in the prognosis of these children, and therefore no palliative treatment after surgery is advocated. Brain stem gliomas account for approximately 10% of all pediatric brain tumours. Cranial nerve signs, ataxia and cerebellar signs with or without symptoms and signs of raised intracranial pressure are classically described symptoms and signs. Radiographic findings and clinical correlates can be used to categorize brain stem tumours into four types: diffuse, focal, exophytic and cervicomedullary. Histologically most brain stem gliomas are fibrillary astrocytomas. Diffuse brain stem gliomas are the most commonly seen tumour in the brain stem. These lesions are malignant high grade fibrillary astrocytomas. Focal tumours of the brain stem are demarcated lesions generally less than 2 cms in size, without associated edema. Most commonly seen in the midbrain or medulla, they form a heterogeneous pathological group, showing indolent growth except when the lesion is a PNET. Dorsally exophytic tumours lie in the fourth ventricle, while cervicomedullary lesions are similar to spinal intramedullary tumours. Expanding lesions are the only lesions amenable for excision while infiltrative and ventral lesions are not.

We report an unusual case of lateral medullary infarction after successful embolization of the vertebral artery dissecting aneurysm (VADA). A 49-year-old man who had no noteworthy previous medical history was admitted to our hospital with a severe headache. Computed tomography (CT) revealed a subarachnoid hemorrhage, located in the basal cistern and posterior fossa. Cerebral angiography showed a VADA, that did not involve the origin of the posterior inferior cerebellar artery (PICA). We treated this aneurysm via endovascular trapping of the vertebral artery distal to the PICA. After operation, CT revealed post-hemorrhagic hydrocephalus, which we resolved with a permanent ventriculoperitoneal shunt procedure. Postoperatively, the patient experienced transient mild hoarsness and dysphagia. Magnetic resonance image (MRI) showed a small infarction in the right side of the medulla. The patient recovered well, though he still had some residual symptom of dysphagia at discharge. Such an event is uncommon but can be a major clinical concern. Further investigation to reveal risk factors and/or causative mechanisms for the medullary infarction after successful endovascular trapping of the VADA are sorely needed, to minimize such a complication.

Purpose

Acute and late changes in magnetic resonance imaging of the pediatric brain have been described after radiotherapy (RT). We report the post-RT neuroimaging changes in the posterior fossa after intensity-modulated RT (IMRT) in children with medulloblastoma and contrast them with those of leptomeningeal disease.

Methods and Materials

We performed a retrospective review of 53 consecutive children with medulloblastoma who were treated with craniospinal RT followed by IMRT to the posterior fossa and chemotherapy between 1997 and 2006.

Results

After IMRT to the posterior fossa, 8 (15%) of 53 patients developed increased fluid-attenuated inversion-recovery signal changes in the brainstem or cerebellum and patchy, multifocal, nodular contrast enhancement at a median of 6 months. The enhancement superficially resembled leptomeningeal disease. However, the enhancement resolved without intervention at a median of 6 months later. The accompanying fluid-attenuated inversion-recovery signal changes occasionally preceded the enhancement, were often parenchymal in location, and resolved or persisted to a lesser degree. All 8 patients with transient magnetic resonance imaging changes in the posterior fossa were alive at last follow-up. In contrast, leptomeningeal disease occurred in 8 (15%) of our 53 patients at a median of 19.5 months after IMRT completion. Of these 8 patients, 7 demonstrated initial nodular enhancement outside the conformal field, and 7 patients died.

Conclusion

Magnetic resonance imaging changes can occur in the posterior fossa of children treated with IMRT for medulloblastoma. In our experience, these transient changes occur at a characteristic time and location after RT, allowing them to be distinguished from leptomeningeal disease.

Introduction

Medulloblastoma is one of the most common pediatric brain malignancies. The usual presenting clinical features are related to posterior fossa syndrome or/and hydrocephalus. Cauda equina syndrome is a very rare presentation for this disease.

Case presentation

We describe the case of a three-year-old boy with cauda equina syndrome as the initial presenting clinical feature for medulloblastoma. He was initially diagnosed as having a spinal tumor by magnetic resonance imaging scan. Subsequently, a cranial magnetic resonance imaging scan revealed a posterior fossa tumor with features of dissemination. He had substantial improvement after treatment. This case report is complemented by a literature review related to this unusual presentation.

Conclusions

Medulloblastoma primarily presenting with cauda equina syndrome is very rare. However, spinal drop metastasis should be considered in the pediatric age group to avoid suboptimal management.

We present the case of a patient with a solitary left frontoparietal brain metastasis of melanoma previously treated with surgery. Three months later, the patient was admitted to the emergency room in a confusional state with meningeal signs. A cerebrospinal fluid (CSF) test and magnetic resonance imaging findings suggested a subarachnoid haemorrhage (SAH) and/or meningeal carcinomatosis. The results of a cytological examination of the CSF showed neoplastic epithelial cells consistent with metastatic melanoma cells. Resection of metastatic posterior fossa lesions is often cited as a risk factor for leptomeningeal dissemination, however, when the resection is limited to the anterior fossa, this complication is relatively rare. In contrast, SAH may be a complication of leptomeningeal dissemination and responsible for acute meningeal syndrome. Treatment with high doses of corticoids did not show any improvement, and intrathecal chemotherapy was not possible due to the patient's poor functional status. She succumbed 1 week after admission.

ABSTRACT

Five unusual cases of posterior skull base tumors were treated through different skull base approaches. Two or more staged operations were required to achieve total or near-total excision and decompression of two extensive tumors. Total excision of an extensive en plaque meningioma of the foramen magnum that encircled the brain stem and cervical spinal cord could not be achieved through the extreme lateral and suboccipital craniectomy approach. However, the vital structures were decompressed and the patient's postoperative morbidity was acceptable. An extended middle fossa approach was required to excise a hemangiopericytoma of the middle and posterior fossae in a 12-year-old. Extension of the tumor into the posterior fossa precluded a retromastoid approach because the mass draped the lower cranial nerves posteriorly. Two men had undifferentiated adenocarcinomas involving the jugular foramen and middle to posterior fossa, respectively. The origin of one was renal in a 37-year-old man. A 63-year-old man survived 1.5 years after a good decompression of his extensive tumor and irradiation. The histological diagnosis of paraganglioma of the occipital bone was a surprise in a 25-year-old man with pure bony involvement. These cases indicate that the appropriate selection of skull base approaches and their combination can provide the needed access to achieve adequate excision or decompression of masses located in challenging anatomical regions of the skull base. Furthermore, good surgical excision improves palliation in radioresistant metastatic tumors of the skull base.





Dermoid tumours in children usually occur in two locations: at the anterior fontanelle and on the occipital squama. An exceptional site of origin for a posterior fossa dermoid cyst is the extradural space. There are only six previous cases of this situation reported in the literature. A series of 103 subscalp and calvarial masses in children were reviewed and three children are reported with extradural dermoids of the posterior fossa, which communicated with the skin through midline occipital dermal sinuses. All three children were seen after the rapid growth or the formation of an abscess in a previously noted occipital subcutaneous mass present since birth. Although computed tomography or magnetic resonance imaging showed the dermal sinus and the intracranial tumour, these studies were unable to ascertain the intradural or extradural nature of the tumours, their exact origin only being established at operation. Histopathological study showed preclinical signs of infection in the two patients that had not yet formed an abscess. It is suggested that early neurosurgical treatment of these neoplasms should be done to prevent the development of severe intracranial infection. The previously reported simplicity of surgical removal of occipital extradural dermoids was not confirmed in this series.



Complete removal of three-compartment trigeminal schwannomas is a challenge to neurosurgeons. To expand exposure of each compartment, the combination and modification of skull base approaches are necessary. The 61-year-old woman was admitted with chronic headache. Preoperative magnetic resonance imaging showed 47×50×40 mm-sized tumor originating primarily in the middle cranial fossa extended to the posterior and the infratemporal fossa. We performed operation in five stage; 1. Zygomatic osteotomy, 2. Inferior temporal fossa plate removal and foramen ovale opening, 3. Cavernous sinus opening, 4. Tailored anterior petrosectomy, 5. Meckel's cave opening. Combination of skull base surgery should be concerned according to the patient. In this study, extradural basal extension with zygomatic osteotomy, interdural posterior extension with tailored anterior petrosectomy, and intracavernous exploration are reasonable options for remodeling three-compartment lesion into a single compartment. Tailoring of bone resection and exploring through natural pathway between meningeal layers accomplish single-stage operation for complete removal of tumors.

Arachnoid cysts are the most common congenital cystic lesions in the brain occurring in the middle fossa, suprasellar region and occasionally in the posterior fossa. Conventionally all cysts are considered as benign and symptoms are attributed to expansion of cysts causing compression of adjacent neurological structures, bleeds within the cyst or due to the development of acute hydrocephalus. We are reporting this case of a 15-year-old female patient with non-progressive weakness in the limbs since the age of seven years who presented with acute onset syncopal attacks and respiratory failure. She was intubated and ventilated. An magnetic resonance imaging scan showed large posterior fossa cyst extending up to mid second cervical vertebra causing compression of the medulla and pons, with mild hydrocephalus. After a failed attempt to wean her from the ventilator a cysto peritoneal shunt surgery was performed following which she was weaned from the ventilator successfully. Weakness in the upper and lower limbs, which had increased in the preceding month, also improved following the surgery.

Objectives

Chiari type II malformation (CII) is a congenital deformity of the hindbrain. The posterior fossa and cerebellum are small in CII. The cerebellar atrophy is associated with cognitive and motor deficits. Brainstem compression occurs in some patients with CII for whom posterior fossa decompression may be life saving. The aim was to determine whether posterior fossa decompression can prevent or reduce the cerebellar atrophy in CII.

Methods

Cerebellar volumes and their tissue types (gray matter, white matter, and CSF volumes) from brain MRI were compared among four CII patients, aged 9.5 to 16.5 years, who had had posterior fossa decompression in infancy, 28 CII patients who had not had posterior fossa decompression, and ten age-matched normal controls. Parametric and non-parametric tests investigated group differences.

Results

Compared to controls, mean cerebellar volume was significantly smaller in CII patients (p<0.0001). Mean CSF volume within the cerebellar fissures and fourth ventricle was significantly smaller in patients without posterior fossa decompression compared to the CII patients who had the decompression, p=0.043. Mean CSF volume of the latter group was similar to the controls. Other cerebellar volumetric measurements did not differ between the CII groups.

Conclusions

Posterior fossa decompression normalizes CSF spaces within the posterior fossa in CII but does not prevent the cerebellar atrophy. The author proposes that surgical expansion of the posterior fossa should be considered in infants with CII who have a significantly small posterior fossa, to prevent or reduce the deficits associated with the cerebellar atrophy.

To the best of our knowledge, the association of a medulloblastoma with a “dural-tail” sign has not been previously reported. A 24-year-old male developed severe headaches and right-sided dysmetria that worsened over 1 month. Magnetic resonance (MR) imaging of the brain demonstrated a heterogeneously enhancing lesion in the posterior fossa. The lesion appeared to be tentortally-based and exhibited a characteristic “dural-tail” sign, which is considered pathognothonic for meningioma. Cerebellar tonsil ectopia and hydrocephalus were also present. The presumptive diagnosis of tentorial meningioma was made. The lesion was resected by a posterior fossa approach. At surgery, the appearance of the tumor was inconsistent with the diagnosis of meningioma, and histopathologic evaluation yielded the diagnosis of medulloblastonia. This case and the literature demonstrate that malignant tumors can present with the characteristic MR imaging appearance of a meningioma. This possibility must be considered when treatment is planned, especially if a nonoperative course is favored.

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Background

PHACE is a neurocutaneous syndrome associated with: Posterior fossa brain malformations, large “segmental” facial hemangiomas, arterial cerebrovascular-, cardiovascular-, and eye anomalies.

Case vignette

We are reporting a girl with PHACE syndrome. The patient had a congenital right-sided facial hemangioma with plaque-morphology. At age 11 years and 2 months she presented with short stature, markedly decreased growth velocity and signs and symptoms suggestive of hypothyroidism. Magnetic Resonance Imaging (MRI) of the brain revealed complex structural and cerebrovascular arterial anomalies, including an empty sella. Testing of pituitary function revealed multiple pituitary dysfunctions, including absolute growth hormone deficiency, hypogonadotropic hypogonadism, central hypothyroidism, and secondary adrenal insufficiency.

Conclusions

This case suggests the necessity to screen all patients with PHACE syndrome and intracranial malformations for pituitary dysfunction at regular intervals.

ABSTRACT

Objective: The aim of this study was to determine the use and safety of the endoscope as an adjunct during trigeminal and facial nerve decompression procedures performed under keyhole conditions in the posterior fossa. Method: We performed 67 surgeries in 65 patients with symptomatic trigeminal and facial nerve compression syndromes. The diagnosis was made mainly on the basis of clinical history, examination, and magnetic resonance imaging scans. Surgery was performed in all cases under endoscope-assisted keyhole conditions. The follow-up was 1 week postoperatively, 6 months, and then yearly up to 7 years. All 34 patients with trigeminal neuralgia received preoperative medication treatment and experienced failure with it. Eighteen patients out of 30 with hemifacial spasm had been previously treated with botulinum toxin injections. One patient suffered from both trigeminal neuralgia and facial spasm, because of a megadolichobasilar and vertebral artery with compression of both cranial nerves. Results: Sixty-four of the 65 patients became symptom free after surgical treatment; one revision surgery was necessary because of disappearance of the decompression muscle piece. No mortalities or minor morbidities were observed in this series. Conclusion: A precise planned keyhole craniotomy and the simultaneous use of the microscope and the endoscope render the procedure of the decompression less traumatic.

A rare case of subependymoma in a young patient presenting with sensory dysesthesia is reported. Computed tomography scan and magnetic resonance imaging revealed a posterior fossa mass occluding the fourth ventricle with infiltration to the right side immediately behind the pontine tegmentum and impinging on the right spinothalamic tract. Postoperative tumor histopathology revealed the classical appearance of subependymoma. Subependymoma is a rare, asymptomatic, slow-growing, low-grade glioma of the central nervous system. If symptomatic, the clinical features are commonly secondary to hydrocephalus, but subependymoma presenting with sensory dysesthesia has never been reported in the literature.

Background:

We describe an unusual presentation of a ruptured aneurysm of the posterior communicating artery with an acute subdural hematoma (SDH) located in the posterior fossa. We also reviewed the literature, focusing on the location of this intracranial hematoma.

Case Description:

An 83-year-old woman was admitted to our institution with recent sudden headache and dizziness. Magnetic resonance imaging showed a thin collection of blood in the subdural space adjacent to the clivus, along the wall of the posterior fossa, and at the cervical spine level. A right posterior communicating artery aneurysm was diagnosed using computed tomography angiography and digital subtraction angiography. The aneurysm had two lobes, one of which was attached to the right dorsum sellae. The aneurysm was occluded by stent-assisted coil embolization. The patient was discharged 3 weeks after admission with absence of neurological deficit.

Conclusion:

A ruptured aneurysm of the posterior communicating artery may cause an acute SDH.

Radiation therapy for medulloblastoma consists of postoperative irradiation of the intracranial and spinal subarachnoid volume with an additional boost to the primary site of disease in the posterior fossa. The entire posterior fossa is usually included in the boost volume. Conformal radiation therapy techniques may be used to boost the primary site alone and substantially reduce the dose received by normal tissues, including the supratentorial brain, the middle and inner ear, and the hypothalamus. Using these techniques to irradiate only the tumor bed or residual tumor and not the entire posterior fossa represents a new paradigm in the treatment of medulloblastoma. In this study, we examine the use of conformal radiation therapy in the treatment of 14 patients with medulloblastoma. These patients were treated with multiple static, individually shaped, noncoplanar beams directed at the primary site after craniospinal irradiation. Excluding two patients who had previously received irradiation to the posterior fossa, the mean dose delivered to the primary site was 5715 cGy. Among the medulloblastoma patients (n = 10) who received immediate postoperative radiation therapy, no failures have occurred with a median follow-up of 42 months (range from 30 to 54 months). To demonstrate the differences in the distribution of dose to normal tissues when comparing conventional and conformal techniques, dose-volume histograms of the total brain, middle and inner ear, hypothalamus, and temporal lobe were created and presented for an example case. The neurologic, neuroendocrine, and neurocognitive outcome for patients with medulloblastoma may be influenced with the use of conformal radiation therapy. The use of these techniques should be formally tested in prospective studies of rigorously staged patients with failure rate monitoring.

AIM—To establish the prevalence of central nervous system (CNS) abnormalities on magnetic resonance imaging (MRI) in a population of children with congenital melanocytic naevi (CMN) over the head and/or spine, and to compare this with clinical findings.
METHODS—Forty three patients identified from outpatient clinics underwent MRI of the brain and/or spine. These were reported by a paediatric radiologist and findings compared with the clinical picture.
RESULTS—Nine patients had abnormal clinical neurology, seven had abnormal findings on MRI, and six had both abnormal clinical and radiological findings. Only three of the abnormal MRIs showed features of intracranial melanosis. Three others showed structural brain abnormalities: one choroid plexus papilloma, one cerebellar astrocytoma, and one posterior fossa arachnoid cyst; the first two of these have not previously been described in association with CMN. The last abnormal MRI showed equivocal changes requiring reimaging.
CONCLUSIONS—The prevalence of radiological CNS abnormality in this group of children was 7/43. Six of these developed abnormal clinical neurological signs within the first 18 months of life, but two did not do so until after the MRI. Two of the CNS lesions were operable; for this reason we support the routine use of early MRI in this group.



OBJECTIVE--To compare computed tomography and magnetic resonance imaging in investigating patients suspected of having a lesion in the posterior cranial fossa. DESIGN--Randomised allocation of newly referred patients to undergo either computed tomography or magnetic resonance imaging; the alternative investigation was performed subsequently only in response to a request from the referring doctor. SETTING--A regional neuroscience centre serving 2.7 million. PATIENTS--1020 Patients recruited between April 1986 and December 1987, all suspected by neurologists, neurosurgeons, or other specialists of having a lesion in the posterior fossa and referred for neuroradiology. The groups allocated to undergo computed tomography or magnetic resonance imaging were well matched in distributions of age, sex, specialty of referring doctor, investigation as an inpatient or an outpatient, suspected site of lesion, and presumed disease process; the referring doctor's confidence in the initial clinical diagnosis was also similar. INTERVENTIONS--After the patients had been imaged by either computed tomography or magnetic resonance (using a resistive magnet of 0.15 T) doctors were given the radiologist's report and a form asking if they considered that imaging with the alternative technique was necessary and, if so, why; it also asked for their current diagnoses and their confidence in them. MAIN OUTCOME MEASURES--Number of requests for the alternative method of investigation. Assessment of characteristics of patients for whom further imaging was requested and lesions that were suspected initially and how the results of the second imaging affected clinicians' and radiologists' opinions. RESULTS--Ninety three of the 501 patients who initially underwent computed tomography were referred subsequently for magnetic resonance imaging whereas only 28 of the 493 patients who initially underwent magnetic resonance imaging were referred subsequently for computed tomography. Over the study the number of patients referred for magnetic resonance imaging after computed tomography increased but requests for computed tomography after magnetic resonance imaging decreased. The reason that clinicians gave most commonly for requesting further imaging by magnetic resonance was that the results of the initial computed tomography failed to exclude their suspected diagnosis (64 patients). This was less common in patients investigated initially by magnetic resonance imaging (eight patients). Management of 28 patients (6%) imaged initially with computed tomography and 12 patients (2%) imaged initially with magnetic resonance was changed on the basis of the results of the alternative imaging. CONCLUSIONS--Magnetic resonance imaging provided doctors with the information required to manage patients suspected of having a lesion in the posterior fossa more commonly than computed tomography, but computed tomography alone was satisfactory in 80% of cases...

To investigate the role of magnetic resonance imaging (MRI) in neurological disorders, 115 children were studied in two groups. Group A (78 patients) was studied by paired computed tomography and MRI cranial scans. Group B (37 patients) was studied by paired computed tomography assisted myelography (CTM) and MRI spinal scans. In group A, the scans were generally equivalent for supratentorial tumours and for investigating fits, hydrocephalus, benign intracranial hypertension, and cerebral atrophies, but MRI scanning was superior for posterior fossa tumours and cysts. In group B, MRI scans were superior for intramedullary spinal tumours, spinal dysraphic problems with tethering or syrinx, and were complementary to CTM in diastematomyelia.

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