Neuroimaging of the optic nerve after fenestration for management of pseudotumor cerebri
L. M. Hamed, D. T. Tse, J. S. Glaser, S. F. Byrne and N. J. Schatz
Bascom Palmer Eye Institute, University of Miami (Fla) School of Medicine.
The mechanisms by which optic nerve-sheath fenestration is effective remain
speculative. Possibilities include surgical production of a cerebrospinal
fluid filtration outlet or scarring in the subarachnoid space around the
nerve in the vicinity of the fenestration site, with shifting of the
pressure gradient from the nerve head to the retrobulbar portion. Two
patients who underwent successful optic nerve-sheath fenestration developed
a cystlike structure contiguous to the fenestration site, apparently in
direct communication with the optic nerve sheaths. This was shown on
magnetic resonance imaging (one patient) and orbital echography (both
patients). These previously unreported observations may support the
hypothesis that fenestration works by creating a filtration apparatus that
controls the intravaginal pressure in the subarachnoid space surrounding
the orbital segment of the optic nerve.
