Dean McGee Eye Institute (JAL), Oklahoma City, Oklahoma; and Ophthalmology Department (RMS), University of Oklahoma, Oklahoma City, Oklahoma, email@example.com
Wilkes and Siatkowski (1) recently reported a 16-year-old girl with idiopathic intracranial hypertension (IIH) who underwent uncomplicated bilateral optic nerve sheath fenestration (ONSF) for worsening vision despite maximal medical therapy. Postoperatively, she continued to lose vision, deteriorating from 20/25, right eye, and 20/40, left eye, on postoperative day 4 to 20/100 in both eyes at postoperative day 14. Repeat lumbar puncture revealed an opening pressure of 65 cm H2O. A ventriculoperitoneal (VP) shunt was performed, but progressive visual loss ensued, to the 20/200 level in each eye at the most recent visit. It was postulated that in patients with IIH with very high intracranial pressure (ICP), abnormal cerebrospinal fluid (CSF) flow producing a compartmentalization syndrome, as described by Killer et al (2), may preclude a good response to ONSF and/or VP shunt.
We recently encountered a similar case of an obese 11-year-old girl with IIH and an opening CSF pressure of >50 cm H2O. She was initially treated with acetazolamide at an outside facility and 5 days later presented to us. Examination revealed marked chronic papilledema with macular exudates and visual acuities of 20/100, right eye, and 20/20, left eye, with profound generalized visual field constriction. Also, she had a right facial and bilateral abducens nerve palsies. The patient was treated with intravenous solumedrol and acetazolamide and scheduled for bilateral ONSF in approximately 24 hours.
Preoperative visual acuities were 20/800, right eye, and 20/50, left eye. One day following uncomplicated surgery, vision was stable in each eye, and on postoperative day 6, visual fields showed persistent generalized constriction and visual acuities were 20/250, right eye, and 20/60, left eye. Two weeks later, she saw her pediatrician because of decreased visual acuity in the right eye but was not seen by an ophthalmologist. Lumbar puncture revealed an opening pressure of 55 cm H2O. The patient underwent VP shunt on postoperative day 14.
Eleven days after VP shunt, visual acuity was light perception, right eye, and 20/60, left eye. Dilated fundus examination showed residual optic disc swelling in both eyes with optic atrophy. Opening pressure on lumbar puncture was 16 cm H2O. Three months after VP shunt, vision measured light perception, right eye, and 20/600, left eye. Dilated fundus examination showed sharp and flat discs with diffuse pallor.
The patient described here and the one previously reported (1) are similar in that they both underwent uncomplicated ONSF, had high ICP (above 55 cm H2O) after ONSF with progressive visual loss, and subsequently underwent VP shunting after which visual acuity continued to decline. Killer et al (2) have reported patients with IIH who underwent ONSF but had persistent papilledema, even after subsequent VP shunting. They suggested that a possible impedance of flow exists between the subarachnoid space of the optic nerve and the intracranial space, speculating that CSF flow may not be bidirectional due to the high pressure (2). Patients with extreme elevations of ICP after ONSF who do not respond to interventions to decompress the optic nerve may have a compartmentalization syndrome sequestering the subarachnoid space and the optic nerve and represent a subgroup of patients with IIH prone to profound visual loss.
Beck and Greenberg (3) described 5 patients with papilledema secondary to intracranial tumors who became blind immediately following decompressive craniotomy. They postulated that lowering the ICP altered local vasoregulatory factors within the optic nerve, reducing perfusion to the ophthalmic artery and prelaminar optic nerve. Any concomitant drop in the systemic blood pressure could exacerbate optic nerve blood flow already compromised by the elevated subarachnoid space pressure. In addition to medically lowering ICP preoperatively, they recommended constant monitoring of blood pressure during surgery in attempt to prevent visual loss after surgery in high-risk patients with papilledema and visual field defects (3). Neither patient described here had periods of hypotension either intra- or postoperatively.
Although most patients with IIH and significant visual loss undergo successful ONSF, some patients may continue to have progressive loss of vision postoperatively. The temporal profile of this visual loss is not consistent with complications from surgery or with abrupt intraoperative reduction of ICP or systemic blood pressure. Our cases suggest that patients with IIH and extremely elevated (>50 cm water) ICP may require more aggressive intervention in order to minimize vision loss. Such patients need strict monitoring of vision and ICP after ONSF. Further reduction of vision after uncomplicated surgery should prompt repeat lumbar puncture. If these patients have persistent and extreme elevation of ICP after ONSF, urgent VP shunt placement should be performed to protect remaining vision, with appropriate preoperative medical lowering of ICP and intraoperative monitoring of systemic blood pressure.
Julie A. Linden, BA
R. Michael Siatkowski, MD
Dean McGee Eye Institute, Oklahoma City, Oklahoma
Ophthalmology Department, University of Oklahoma, Oklahoma City, Oklahoma firstname.lastname@example.org
1. Wilkes BN, Siatkowski RM. Progressive optic neuropathy in idiopathic intracranial hypertension after optic nerve sheath fenestration. J Neuroopthalmol. 2009;29:281-283.
2. Killer HE, Jaggi GP, Flammer J, Miller NR, Huber AR, Mironov A. Cerebrospinal fluid dynamics between intracranial and the subarachnoid space of the optic nerve. Is it always bidirectional? Brain. 2007;130:514-520.
3. Beck RW, Greenberg HS. Post-decompression optic neuropathy. J. Neurosurg. 1985;63:196-199.
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