Optic nerve sheath fenestration: Current status in France and comparison of 6 different surgical approaches

PURPOSE

Optic nerve sheath fenestration (ONSF) is a surgical procedure commonly performed in the Anglo-Saxon countries for the treatment of medically refractory idiopathic intracranial hypertension (IIH). We chose to compare 6 different trans-orbital surgical approaches to ONSF. We also desired to determine the number of optic nerve decompression procedures performed in France in 2019 and 2020.

METHODS

Four fresh frozen orbits were dissected at the University of Nice anatomy laboratory. We performed the following surgical approaches: (i) eyelid crease, (ii) lid-split, (iii) medial transconjunctival with medial rectus disinsertion, (iv) medial transconjunctival without rectus disinsertion, (v) lateral transconjunctival and (vi) lateral orbitotomy. For each surgical approach, we measured the distance between the incision and the optic nerve dura mater. We also extracted data from the French National PMSI (Programme de Médicalisation des Systèmes d' Information) database from January 2019 through December 2020 to determine the annual number of optic nerve decompression procedures.

RESULTS

The lid crease and medial transconjunctival approaches provided the shortest distance to the optic nerve (average 21mm and 24mm, respectively) and the lowest levels of difficulty compared to the other surgical routes. A total of 23 and 45 optic nerve decompressions were performed in France in 2019 and 2020, respectively. Among them, only 2 and 7 procedures, respectively, were performed through a trans-orbital approach.

CONCLUSION

Upper lid crease incision and medial transconjunctival approaches are the most direct and easiest surgical routes when performing an ONSF. We found that ONSF was rarely performed in France. We strongly recommend close cooperation between ophthalmologists, neurologists, neurosurgeons and interventional radiologists.

[Idiopathic intracranial hypertension: From physiopathological mechanisms to therapeutic decision]

Clinical features include visual disturbances, headaches, and pulsatile tinnitus that can be associated with reduced quality of life, and a risk of irreversible visual impairment in some cases. Obese women of childbearing age represent the main at-risk population, and the incidence of the disease is increasing because of rising prevalence of obesity worldwide. In addition, an imbalance in sex hormones is reported as a contributing risk factor. The pathophysiology of idiopathic intracranial hypertension involves a disturbance of the evacuation pathway of intracranial fluids caused by the increase in intracranial venous pressure. Brain imaging is useful for diagnosis with several signs including bilateral stenosis of the transverse sinuses that plays a major role in the pathogenesis of the disease by creating a positive feedback loop that increases intracranial venous hypertension and contributes to clinical manifestations. Treatment aims to relieve symptoms and prevent permanent visual impairment. Drug therapies including acetazolamide and topiramate have moderate effectiveness. Among invasive treatments, transverse sinus stenting seems to be the most interesting option to consider in drug-resistant patients. Weight loss remains essential to achieve a sustainable improvement by reducing central venous pressure. Future randomized trials are expected to reach a consensus on this treatment.

[Idiopathic intracranial hypertension and factor V Leiden mutation]

Activated proteinC resistance is a frequent prothrombotic abnormality. In most cases it is due to factorV Leiden mutation by nucleotide G1691A substitution. This recently described thrombophilic defect of activated proteinC resistance has been postulated to be implicated in the pathogenesis of idiopathic intracranial hypertension (IIH). We report a case of factorV Leiden mutation in association with IIH and their likely link and implication in the management of IIH.

[Sixth, seventh and tenth cranial nerve palsies associated with pseudotumor cerebri in a 13-year-old boy]

We describe the case of a 13-year-old boy who presented to the emergency department with an acute onset paresis of the left abducens, facial and vagus nerves. Bilateral papilledema was seen on fundoscopy. Blood tests and brain magnetic resonance imaging and angiography showed no abnormalities. A lumbar puncture revealed an elevated intracranial pressure (575mmH2O) and clear cerebrospinal fluid. The diagnosis of pseudotumor cerebri (PTC) associated with multiple cranial nerve palsies was made. Treatment with acetazolamide was initiated, resulting in progressive improvement with no sequelae and no clinical recurrence over an 8-month follow-up period. PTC in children can present with a wide spectrum of neurological signs, especially cranial nerve palsies which are most likely related to a pressure-dependent stretching mechanism. In 2007, distinctive diagnostic criteria for pediatric PTC were established, including the presence of any cranial nerve palsy in the absence of an identifiable etiology.