Sudden blindness after ventriculography. Bilateral retinal vascular occlusion superimposed on papilledema

Permanent Visual Loss as a Complication of Decompressive Surgery for the Treatment of Posterior Fossa Tumours: A Report of Two Cases

Posterior fossa tumours are one of the most common types of solid neoplasia in paediatric patients. Although impaired vision can occur at presentation, it usually stabilises or improves after decompressive surgery. However, cases of permanent and profound visual loss have been reported following successful tumour resection, despite receiving little attention from the medical community. In this paper, we present two cases of young patients who experienced severe and permanent visual loss following uncomplicated surgery for posterior fossa tumour removal. We discuss the possible mechanism involved in the visual loss and measures to prevent such a dreadful complication.

Post-craniotomy blindness in the supine position: Unlikely or ignored?

Immediate visual loss following craniotomy in the supine position is a disastrous complication in neurosurgical patients. The incidence is unknown and little is known on the definite pathogenesis. Also, preventive or restorative interventions are unclear. We describe the rare case of post-craniotomy optic neuropathy and sudden visual loss after craniotomy in the supine position for an olfactory groove meningioma, discuss the possible pathophysiology and review the literature on the pathogenesis, risk factors, and outcome. Although rare, neurosurgeons, as well as neuroanesthesiologists should be aware of the possibility of this devastating complication in the high-risk group of patients.

Shunt failure without ventriculomegaly proclaimed by ophthalmic findings

Four patients who developed increased intracranial pressure from ventricular shunt failure suffered a delay in diagnosis because magnetic resonance imaging of the brain did not show ventriculomegaly and because ophthalmic findings were initially overlooked or misinterpreted. None of the patients had the conventional manifestations of shunt failure: severe headache, nausea, vomiting, and depressed consciousness. Three patients suffered marked, permanent vision loss from chronic papilledema. These cases affirm that increased intracranial pressure may occur in shunt dependency without producing either conventional clinical symptoms or signs on imaging of the brain. Because ophthalmic manifestations may be the major clues to diagnosis, and because irreversible loss of vision is possible if these clues are overlooked, consideration should be given to periodic ophthalmological examination of shunt-dependent patients.

Benign intracranial hypertension: visual loss and optic nerve sheath fenestration

Five patients with serious ocular complications of benign intracranial hypertension are described. Optic nerve sheath fenestration resulted in resolution of papilloedema with, in three instances, improvement in vision. Benign intracranial hypertension may not always be benign for vision and fenestration operations may prevent or reverse visual deterioration by an effect on the optic nerve rather than by reducing intra-cranial pressure.

Post-decompression optic neuropathy

Blindness resulting from a decompressive craniotomy is uncommon. Five patients with intracranial tumors and papilledema who developed a bilateral optic neuropathy during an apparently uncomplicated craniotomy are presented. Symptoms of visual field loss were minimal preoperatively in four. Visual recovery in general was poor. The nerve fiber bundle pattern of visual field loss in these cases implicates the optic disc as the site of damage in this disorder. It is postulated that hypoperfusion to the prelaminar portion of the optic nerve is the underlying cause.

Abnormal electroretinograms and visual evoked potentials in chronic papilledema using time-difference analysis

Visual function is usually considered to be normal in papilledema. We report previously undescribed abnormalities in the electroretinograms (ERG) and visual evoked potentials (VEP) of two patients with chronic papilledema. The steady-state latencies of the ERG and VEP were calculated using time-difference analysis. The ERG was abnormal under both scotopic (slow) and photopic (fast) flicker conditions, but the VEP was abnormal only to fast flicker photopic stimulation. This may indicate a relative vulnerability of a high frequency signal system under conditions of raised intracranial pressure. The abnormalities resolved rapidly once the intracranial pressure had been normalised. The cause of the VEP and particularly the ERG abnormalities remains unknown.

Retinal arterial obstruction in children and young adults

The records of 27 patients who developed retinal arterial obstruction (RAO) prior to the age of 30 years were studied to ascertain associated systemic and ocular findings as possible etiologic factors. A history of migraine was found in approximately one third of the patients, and coagulation abnormalities wer also common. Trauma, sickle cell hemoglobinopathies, cardiac disorders, use of oral contraceptives, pregnancy, systemic lupus erythematosus and intravenous drug abuse were less frequently encountered. Ocular abnormalities included increased intraocular pressure, subtle buried drusen of the optic nerve head and a congenital prepapillary arterial loop. In contrast to older patients with RAO, there was no clinical evidence of atheromatous disease. In most patients, one or more systemic or ocular etiologic factors could be discerned. Whereas etiologic relationships may be multifactorial and generally differ from those commonly found in older patients with RAO, the visual prognosis in younger and older patients appears to be similar.

Blindness following tentorial herniation

In seven patients, permanent bilateral visual loss was the chief neurological residual following relief of tentorial herniation. The causes of herniation were unilateral subdural hematoma in three patients and bilateral subdural hematomas, bilateral subdural empyemas, traumatic intracerebral hematoma, and postoperative infarction in one patient each. Three patients, including two with occipital infarction documented by computed tomographic scan, developed optic atrophy, indicating that both pregeniculture visual pathway damage and posterior cerebral artery compression occurred. Increasing availability of computed tomographic scanning should help eliminate this rare cause of blindness by facilitating earlier diagnosis of supratentorial masses.