Metamorphopsia and permanent cortical blindness after a posterior fossa tumor

Symptomatic cerebral vasospasm following posterior fossa hemangioblastoma resection: illustrative case

BACKGROUND

Symptomatic cerebral vasospasm following posterior fossa intra-axial tumor resection is a rare phenomenon with only seven cases previously reported in the literature. The condition appears distinct to vasospasm following supratentorial tumor resection and extra-axial tumor resection of the posterior fossa. It shares, however, similarities with vasospasm following aneurysmal subarachnoid hemorrhage.

OBSERVATIONS

The authors describe their experience with a 23-year-old female who developed delayed symptomatic vasospasm following resection of a left parapontine cerebellar hemangioblastoma. Tumor resection was complicated by rupture of a fragile arterialized vein, resulting in significant hemorrhage. The patient developed several episodes of focal and variably reversible neurological deficit. These clinical signs corresponded with angiographically confirmed vasospasm, which responded to standard therapies for vasospasm post aneurysmal subarachnoid hemorrhage.

LESSONS

This case and literature review highlight that symptomatic vasospasm is a rare, potentially highly morbid complication of posterior fossa intra-axial tumor resection. This phenomenon may be related to significant intraoperative or postoperative hemorrhage. Postoperative radiological findings such as high risk modified Fisher scale hemorrhage could alert clinicians to this condition.

Basilar Artery Vasospasm as a Cause of Post-Operative Cerebellar Mutism Syndrome

Post-operative cerebellar mutism syndrome (CMS), also known as posterior fossa syndrome (PFS), is a well-recognized and frequent complication of surgery for posterior fossa tumours in children and young people. Its incidence varies between 8 and 31%, and the pathophysiological mechanisms of delayed onset and resolution of cerebellar mutism are not clear, but axonal damage, oedema, and perfusion defects may be involved. Magnetic resonance imaging has failed to reveal a universal anatomical substrate or a single definite mechanism of injury. We present a case of 16-year-old boy who developed CMS three days after resection of a medulloblastoma, a primary fourth ventricular tumour. Early post-operative imaging showed bleeding in the posterior fossa which required evacuation. CT angiography seven days after surgery demonstrated basilar artery vasospasm. Magnetic resonance brain angiography confirmed persistent narrowing of a segment of the basilar artery closely related to a left cerebellopontine (CP) angle peri-operative haematoma. The patient was treated with nimodipine and hypervolemia. The patient started vocalisation without speech five days later with reversal of radiological lesions. Further recovery of post-operative neurological deficits occurred over a protracted period of several months. This case represents a rare cause of post-operative CMS, with rapid initial recovery that occurred after specific treatment directed at the cause. To our knowledge, this is the first reported case showing mutism associated with basilar artery vasospasm with imaging evidence. This case may suggest the need to undertake urgent vascular imaging in selected cases of post-operative CMS.

Posterior fossa syndrome following brain tumour resection: review of pathophysiology and a new hypothesis on its pathogenesis

INTRODUCTION

Posterior fossa syndrome (PFS), also known as cerebellar mutism syndrome (CMS), is a severe complication affecting children following surgery for posterior fossa brain tumours. Its incidence varies between 8 and 31 %, and its exact pathogenesis remains unclear. In this article, we aim to review the existing theories on its pathogenesis and propose a new hypothesis.

DISCUSSION

There is varying level of evidence on existing theories on the pathogenesis of PFS following surgery. These include cerebellar perfusion deficits due to vasospasm, oedema or axonal injury due to direct surgical injury and neuronal dysfunction. There is emerging evidence that interruption of the dentato-thalamo-cortical (DTC) pathway is responsible for PFS. Based on our experience with intraoperative MRI, radiological and pathological evidence on heat-related brain injury, we propose a new hypothesis implicating thermal injury resulting from the use of the Cavitron Ultrasonic Aspirator (CUSA) as an important mechanism in the pathogenesis of PFS.

CONCLUSION

The pathogenesis of PFS is likely to be multifactorial with direct injury from surgery being a major factor. We believe that thermal injury in addition to mechanical injury to the proximal segment of the DTC plays an important role in the pathogenesis of PFS and should be considered in future research related to the aetiology, prevention and management of PFS.

Symptomatic anterior cerebral artery vasospasm after brainstem hemangioblastoma resection. A case report

Diffuse cerebral vasospasm is a rare complication after brain tumour resection as opposed to that following an aneurysmal subarachnoid haemorrhage. Sellar tumours are among the most common pathologies and locations associated with this complication. Removal of posterior cranial fossa lesions is uncommonly associated with vasospasm, with only nine reported cases. We describe a case of diffuse symptomatic vasospasm mainly involving the right anterior cerebral artery, angiographically confirmed, after resection of a haemangioblastoma of the medulla in an adult patient with von Hippel-Lindau disease. The possible pathogenesis of this phenomenon is discussed.

Vasospasm following tumor removal: report of 5 cases

Cerebral vasospasm is a clinical/angiographical condition frequently observed after a subarachnoid hemorrhage due to the rupture of an intracranial aneurysm. Twenty cases of vasospasm observed after the removal of cerebral tumors have been reported in the literature; we here report on a further five. The time of onset of symptomatic vasospasm was 3-7 days after surgery; three of the patients died of an ischemic event induced by the vasospasm and two survive. Although no angiographic confirmation was obtained in our cases, serial transcranial Doppler (TCD) flow velocities were always high. It is suggested that the TCD-revealed accumulation of blood in the basal cisterns observed in all cases may have been responsible for this unusual condition, and it is therefore important to consider vasospasm as a probable etiological cause of clinical deterioration in patients undergoing the surgical removal of a cerebral tumor. For this reason, whenever any neurological deterioration occurs in such patients, it is advisable to perform TCD in order to verify the presence of any vasospasm and promptly commence suitable treatment.

Cortical blindness in children: a study of etiology and prognosis

Thirty-four children (20 boys, 14 girls) with congenital and acquired cortical blindness were analyzed for visual outcome in relation to etiology, visual evoked potentials, electroencephalography, and cranial computed tomography. All 7 children with congenital cortical blindness remained blind on subsequent examination. Of the 27 children with acquired blindness, 16 (59%) had poor visual outcome. Poor visual outcome occurred in those with cardiac arrest, hypoxia, status epilepticus, intracranial hemorrhage, cerebral thrombosis, and head trauma. Good visual outcome occurred in children with hypotensive episodes after cardiac surgery. Of the 12 children with recovery of vision, the interval from acute loss of vision to partial or total recovery was 2 weeks to 5 months. Seven children had complete recovery of vision with no residual visual field defect. The majority of children (87%) had focal or multifocal spike-and-waves and slow sharp-wave discharges on electroencephalography. None had photic recruitment response or occipital spike-and-wave discharges. Flash visual evoked potential studies performed during acute episodes of cortical blindness documented 11 with absent response, 10 with bilateral increases in latency, and 6 with normal responses. There was no correlation between normal visual evoked potentials and a good visual outcome. Only 2 of 6 children with normal responses had normal vision. Abnormal or absent responses are more predictive of a poor recovery of vision because only 3 of 21 (14%) had normal vision on subsequent examination. Abnormal electroencephalographic findings with focal or multifocal spike-and-wave discharges or cerebral atrophy on cranial computed tomography are also poor prognostic signs.