Bilateral optic neuropathy following unilateral retrobulbar anaesthesia: a case report
- 1Department of Neurology, The Canberra Hospital, Canberra, Australian Capital Territory, Australia
- 2Australian National University Medical School, Canberra, Australian Capital Territory, Australia
- 3The Canberra Eye Hospital, Canberra, Australian Capital Territory, Australia
- Correspondence to Dr Kate E Ahmad, Department of Neurology, The Canberra Hospital, PO Box 11, Woden; Canberra, ACT 2606, Australia;
- Received 28 October 2012
- Revised 9 December 2012
- Accepted 19 December 2012
- Published Online First 19 January 2013
An 82-year-old man was referred with acute bilateral visual loss. He had multiple vascular risk factors and was taking warfarin.
On the day of presentation, he had been admitted elsewhere for elective extraction of a right-sided cataract. Retrobulbar anaesthesia comprised a single injection of 4 ml of 1% lignocaine/2% ropivacaine using a 38 mm 25-gauge needle inserted into the infero-temporal orbit, aiming for the peribulbar space. Fifteen minutes after anaesthesia, he complained of complete loss of vision.
Formal examination demonstrated no perception of light in either eye. Anterior chambers and fundi were unremarkable. There was no pupillary response to light in the right eye, and only a very sluggish response in the left eye. Extraocular movements were globally impaired on the right in keeping with the intended effect of the anaesthetic agents. There was no other neurological deficit.
Twenty minutes after arrival, the patient noticed return of light perception in both eyes. His vision continued to improve and had returned to baseline after approximately 3 h. His extraocular muscles and pupils returned to normal over a similar period.
The patient underwent an urgent CT brain scan which showed air within the right optic nerve (figure 1A,B) but no evidence of acute ischaemia or haemorrhage in brain or orbits. The final diagnosis was iatrogenic bilateral amaurosis due to anaesthetic infiltration of the right optic nerve.
This patient sustained transient bilateral visual loss following unilateral retrobulbar anaesthesia. Granted that he was a vasculopath, it was possible that the visual loss was due to transient ischaemia of both occipital lobes.
However, several things suggest that the visual loss was due to bilateral optic neuropathy. First, the lack of normal pupillary response in either eye would not be expected from a lesion of the occipital cortices. Second, the visible air in the optic nerve implied that the optic nerve sheath had been breached by the injection. Visual loss can occur in the contralateral eye following peri- or retrobulbar anaesthesia1 ,2 and oculomotor nerve palsies and brainstem-mediated loss of consciousness have also been reported.3 ,4 The mechanism is thought to involve tracking of the anaesthetic back along the nerve via either the subdural or subarachnoid space to the optic chiasm, the contralateral optic nerve or the brainstem.1 Tracking of contrast in this way has been demonstrated radiographically.5 The diagnosis of anaesthetic-induced optic neuropathy is usually presumptive because imaging is normal. Our case was unusual in that air was clearly demonstrated in the optic nerve on CT scan, confirming that the optic nerve sheath had been breached.
Third, the time course of recovery (about 3 h) was similar to that described in previous reports of anaesthetic-induced optic neuropathy and similar to the normal rate of recovery from peri- and retrobulbar anaesthesia. There have, incidentally, been no reported cases of permanent deficit following anaesthetic-induced optic neuropathy.
Reports of pneumatisation of the optic nerve are infrequent. Most reports occur in association with trauma.4 ,6 We have found only one other case of retrobulbar anaesthesia associated with a radiologically-visible air bubble2 and suggest that optic nerve involvement may be an under-reported complication of retrobulbar anaesthesia.
Contributors KA wrote the initial manuscript and coordinated the report. DCMc reviewed and edited the manuscript. MD reviewed and edited the manuscript, providing the ophthalmological details. CL reviewed and edited the manuscript and wrote the clinical question.
Competing interests None.
Patient consent Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statements This is a Neurological picture, not a research article. We consent to information from the case to be shared as the JNNP sees fit.