The effect of optic nerve sheath decompression on CSF dynamics in pseudotumour cerebri and related conditions

Optic nerve sheath fenestration for treating papilloedema in the era of cerebral venous sinus stenting

BACKGROUND

Pseudotumour cerebri (PTC) is the syndrome of intracranial hypertension without intracranial mass or hydrocephalus and is the commonest cause of papilloedema seen in many eye clinics. In the last 10 years, we have increasingly used TSS in patients whose papilloedema was not well controlled with medical treatment and have done fewer ONSFs. Here, we review our experience at Royal Prince Alfred Hospital Sydney with ONSF in 35 patients over the period 2002-2021.

METHODS

Retrospective case series of 35 patients, 30 of whom had primary PTC [i.e., idiopathic intracranial hypertension (IIH)] and 5 with secondary PTC.

RESULTS

Eighteen patients had bilateral ONSF and 17 patients unilateral ONSF, in each case of the worse eye. Thirteen patients then underwent transverse sinus stenting (TSS), in each case following ONSF. The primary outcome measures were visual acuity (VA) and mean deviation (MD) on visual field (VF) testing. MD improved by 5 dB or more in 34 of 70 total eyes (48.6%); VA improved by 0.2 logMAR (two lines on Snellen chart) or more in 21 eyes (30%), and by both in 15 eyes (21.4%). Final MD was -10 dB or better in 38 eyes (54.3%); final VA was 0.3 (6/12) or better in 54 eyes (77.1%), and both in 39 eyes (55.7%).

CONCLUSIONS

The results confirm that ONSF can relieve papilloedoema in both eyes and improve both VF and VA, even in cases of fulminant PTC with severe acute visual impairment.

Malignant meningitis presenting as pseudotumor cerebri

Malignant leptomeningitis can present as the clinical syndrome of pseudotumor cerebri due to infiltration of arachnoid villi in the superior sagittal sinus. We show that malignant pachymeningitis can also present with pseudotumor cerebri, likely due to cerebral venous hypertension from transverse sinus compression. We present 3 cases of pseudotumor cerebri due to pachymeningeal or leptomeningeal metastases and discuss the mechanism of intracranial hypertension in such cases, its diagnosis and treatment.

Idiopathic intracranial hypertension (pseudotumor cerebri): recognition, treatment, and ongoing management

OPINION STATEMENT

Idiopathic intracranial hypertension (IIH, pseudotumor cerebri) is a syndrome of elevated intracranial pressure of unknown cause that occurs predominantly in obese women of childbearing age. It is a diagnosis of exclusion and, therefore, other causes of increased intracranial pressure must be sought with history, imaging, and cerebrospinal fluid examination before the diagnosis can be made. IIH produces symptoms and signs of increased intracranial pressure, including papilledema. If untreated, papilledema can cause progressive irreversible visual loss and optic atrophy. The treatment approach depends on the severity and time course of symptoms and visual loss, as determined by formal visual field testing. The main goals of treatment are alleviation of symptoms, including headache, and preservation of vision. All overweight IIH patients should be encouraged to enter a weight-management program with a goal of 5-10 % weight loss, along with a low-salt diet. When there is mild visual loss, medical treatment with acetazolamide should be initiated. Other medical treatments can be added or substituted when acetazolamide is insufficient as monotherapy or poorly tolerated. When visual loss is more severe or rapidly progressive, surgical interventions, such as optic nerve sheath fenestration or cerebrospinal fluid shunting, may be required to prevent further irreversible visual loss. The choice of intervention depends on the relative severity of symptoms and visual loss, as well as local expertise. At present, the role of transverse venous sinus stenting remains unclear. Although there are no evidence-based data to guide therapy, there is an ongoing randomized double-blind placebo-controlled treatment trial, investigating diet and acetazolamide therapy for IIH.

Cranial venous outflow obstruction in the pseudotumour syndrome: incidence, nature and relevance

This study reports a retrospective analysis of the evidence of cranial venous outflow pathology in 188 patients with pseudotumour syndrome (PTS) investigated over the period 1968-1999. Standard methods of investigation appropriate to the period were used, i.e. cerebral angiography, CT and MR scanning. Recently, some patients had specific venous studies including intraluminal cranial venous sinus pressure measurements. A sub-group (25 patients) was investigated for haematological abnormalities. The overall incidence of cranial venous outflow abnormality was 19.7% (37 cases). In decades, related to the predominant investigative method, the figures were: to 1979, 4.2% (2 cases); to 1989, 15.0% (8 cases); to 1999, 31.0% (27 cases). A cause of the venous abnormality was identified in 20 cases, most commonly haematological and iatrogenic. In 17 patients (all females) no cause was identified. Fifteen of the 25 patients (60%) tested specifically were found to have a haematological abnormality, although no correlation was shown between this and a demonstrable venous outflow abnormality. The conclusion was drawn that there is a high incidence (close to one-third) of venous outflow abnormalities in PTS with detailed investigation. Issues of mechanism and therapy are discussed.