Ian H. Johnston

Vein of Galen malformation: diagnosis and management

The vein of Galen malformation is a midline arteriovenous fistula with aneurysmal dilatation of the vein of Galen. The clinical details of diagnosis and treatment in 13 patients with such lesions together with a review of 232 cases collected from the literature are presented in this report. There were 132 males, 77 females, and 36 cases in which the sex was not stated. Eighty patients presented as neonates, 82 were 1 to 12 months old, 39 were 1 to 5 years old, 22 were 6 to 20 years old, and 22 were over the age of 20. The most common presenting symptoms were congestive cardiac failure (110 cases), raised intracranial pressure secondary to hydrocephalus (94 cases), cranial bruit (57 cases), focal neurological deficit (37), seizures (26 cases), and hemorrhage (25 cases). The most characteristic vascular supply to the midline fistula involved multiple bilateral vessels, although bilateral posterior cerebral and unilateral posterior cerebral supply was relatively common. The overall figures for treatment and outcome showed that 91 patients (37.1%) were treated by direct operation and 29 patients (11.3%) were treated by other forms of operation, predominantly shunting or remote vessel ligation. Forty-six patients (18.8%) were treated by medical means (digoxin, diuretics, and ventilatory support). In 79 patients (22.2%), there was no treatment or no details of treatment were available. There was an overall series mortality of 55.6% (no details were available in 33 cases) and a 37.4% mortality for surgically treated cases. After operation, there was a 46.3% incidence of significant morbidity in surviving patients. Neonatal patients fared worst, with an overall mortality of 64 of 70 cases (91.4%) where details were available. The outcome was equally bad for surgically and conservatively treated cases. Operation in the 1- to 12-month age group was more successful, but still carried a mortality of 31.7%, with a significant morbidity in approximately half of the surviving patients. Over the age of 1 year, the surgically treated patients had a 25.6% mortality and a 42.3% major morbidity in survivors. Consideration is given to some of the ways in which these figures may be improved, in particular a staged approach during the neonatal period, with the use of selective embolization or occlusion of vessels to reduce the volume of the arteriovenous shunt until the patient is older and better able to tolerate major operation.

Fluid dynamics of the cerebral aqueduct.

Despite a multitude of theories describing the mechanics of the intracranial spaces in diseases such as hydrocephalus, little is known about the mechanics of normal CSF flow. A pressure difference is required to drive CSF flow. Knowing that the pressure difference driving fluid through the aqueduct is beyond the resolution of clinically used pressure transducers, a computational fluid dynamics program was used to analyze flow through an aqueduct shape. Flow through this duct was compared with that through a cylinder and through a double hourglass. Both steady and oscillating flows were tested, revealing that only 1.1 Pa of pressure is required to move CSF through the aqueduct. This suggests that normally less than 5% of the total resistance to CSF flow within the CSF pathways occurs in the aqueduct.

The treatment of benign intracranial hypertension: A review of 134 cases

Abstract The treatment of benign intracranial hypertension in 134 patients is reviewed. No treatment was required in 16 patients, although the diagnosis may have been doubtful in a number of these. Serial lumbar punctures had only a 38.8% success rate when used alone. Steroids were effective as primary treatment in 81.1% of the patients, although recurrence (13.5%) and complications of therapy were significant in this group. Subtemporal decompression was relatively ineffectual, particularly on the measured cerebrospinal fluid (CSF) pressure. CSF shunting, especially lumboperitoneal, was very effective, although complications were important. The basis of treatment in benign intracranial hypertension is reviewed in light of the current theories of its pathogenesis.

Intracranial pressure changes in craniostenosis

Intracranial pressure changes occurring in patients with craniostenosis were studied by continuous monitoring of intracranial pressure in 20 children. Although clinical or radiologic evidence of intracranial hypertension was present in only one patient, 13 (65%) had persistent or episodic raised intracranial pressure. Intracranial hypertension occurred with involvement of both single and multiple sutures and in four of six patients with hydrocephalus and craniostenosis. Recordings after surgical treatment in nine patients revealed that several months elapsed before intracranial pressure improved significantly or returned to normal, despite apparently adequate bony decompression. This study confirms that continuous monitoring of intracranial pressure adds significantly to clinical assessment in determining the need for, and the efficacy of, surgical treatment in craniostenosis.

Concurrent Pineoblastoma and Unilateral Retinoblastoma: A Forme Fruste of Trilateral Retinoblastoma?

A 10-month-old boy who presented with strabismus and symptoms of intracranial hypertension was found to have a pineoblastoma and a unilateral ocular retinoblastoma. Despite enucleation of the eye, subtotal removal of the pineoblastoma, and craniospinal axis irradiation, the patient died 6 months later from disseminated intracranial neoplasm. As there was no clinical evidence of bilateral retinoblastoma, this case may represent a forme fruste of the trilateral retinoblastoma complex. The clinicopathological features of this unusual syndrome are reviewed.

Meningoceles and the tethered cord syndrome

This study shows that there is a relationship between simple meningocele and the tethered cord syndrome. Two groups of patients were examined: the first comprised patients presenting with neurological abnormality at some period after initial closure of a simple meningocele, and the second group (18 patients) had elective myelography after closure of a simple meningocele in the neonatal period (in 17 of the 18 cases). Of these 18 cases, 10 showed an intradural abnormality, and all underwent surgery confirming their myelographic diagnosis. The conclusion is drawn that after closure of a simple meningocele in the neonatal period, patients should have elective myelography in the first 12 months of life to determine whether or not the tethered cord syndrome is likely to develop during the period of growth.

The definition of a reduced CSF absorption syndrome: A reapraisal of benign intracranial heperetension and related conditions

Abstract A reduced cerebrospinal fluid (CSF) absorption syndrome has been defined by considering the factors controlling CSF absorption, the pressure gradient between the subarachnoid space and the superior sagittal simus (P csf − P ss ), and the resistance to flow across the absorptive channels (R av ). The hypothesis is advanced that this represents the underlying defect in the syndrome previously described by various terms including benign intracranial hypertension, pseudotumour cerebri, otitic hydrocephalus and others. The clinical evidence is reviewed and appears to favour an increase in CSF volume secondary to impaired absorption as the cause of the intracranial hypertension in this syndrome. In addition, known aetiological agents have been shown experimentally to cause significant reductions in CSF absorption. Clinically the syndrome may be produced by any factor which increases either P ss or R av . If this hypothesis is confirmed by further clinical and experimental studies it is suggested that the general term ‘reduced CSF absorption syndrome should replace ‘benign intracranial hypertension and similar terms.

Hydrocephalus and pseudotumour cerebri in the mucopolysaccharidoses

This paper reports two cases of cerebrospinal fluid circulation disorder in children with mucopolysaccharidosis. One patient developed pseudotumour cerebri and the other communicating hydrocephalus. It is suggested that both have a similar underlying abnormality of cerebrospinal fluid absorption with different modes of presentation.

Pseudotumor syndrome in treated arachnoid cysts

We report three patients with arachnoid cysts treated by cyst-peritoneal shunting in whom intracranial hypertension occurred during episodes of shunt malfunction. In one case this was associated with re-expansion of the arachnoid cyst, whilst in the other two cases this did not occur. The similarities between these two cases and patients with pseudotumor cerebri suggest a common pathogenic mechanism — specifically, a disturbance of the cerebrospinal fluid circulation.

Dural sinus thrombosis: a mechanism-based classification and review of 42 cases.

Cranial venous outflow obstruction due to dural sinus thrombosis may result in venous hypertension, cerebral infarction, cerebral haemorrhage or impaired cerebrospinal fluid (CSF) absorption with consequent pseudotumour syndrome. We propose a mechanism based classification of dural sinus thrombosis from these four outcomes. Forty two cases of dural sinus thrombosis presenting to Royal Prince Alfred Hospital between 1986-1997 were retrospectively reviewed. These cases were classified according to mechanism of presentation and relevance of this to site of thrombosis, treatment and prognosis. This study shows that the superior sagittal sinus and transverse sinus are the commonest sites of thrombosis, and multiple sites of thrombosis (69%) are more frequent than a single site. Magnetic resonance imaging (MRI) with venous flow studies is the investigation of first choice for diagnosis but angiography remains the gold standard. A pseudotumour syndrome is the commonest presentation (43%) followed by cerebral haemorrhage (31%). The overall prognosis for sinus thrombosis is good, with 71% of cases recovering to normal function.