Preexisting Ocular Motor Palsy and Central Neuroaxial Block: A Reply to Dr Nair
We read with interest the comments of Dr Abhijit S. Nair1 regarding our recent review in Regional Anesthesia and Pain Medicine concerning ocular motor palsy after spinal puncture.2 We thank him for his interest in our work.
In our work for a study published in 2014,3 we did not observe any case of ocular motor palsy after spinal anesthesia in 60 patients. In this study, we conducted a neuro-ophthalmologic examination before surgery, with postoperative follow-up. We were unable to find any ocular motor palsy that could otherwise have gone unnoticed in the usual practice. Therefore, we conclude that the incidence of ocular motor palsy after subarachnoid anesthesia is low. The question remains, however, what must be done if ocular motor palsy is present prior to anesthesia. Should spinal or general anesthesia be chosen?
In his letter to the editor,1 Dr Nair refers to a case previously published by himself and Kumar4 about a full-term pregnant woman with a preexisting palsy of abducens nerve, secondary to acute petrositis. The patient underwent a cesarean delivery with general anesthesia. According to the authors, subarachnoid anesthesia was precluded to avoid exacerbating the preexisting palsy or affecting other oculomotor nerves (III and IV).4
With this clinical case, they suggest that there is a preferred anesthetic approach when ocular motor palsy exists. Currently, however, there is no guide or protocol available to follow in this circumstance. In fact, after an extensive literature review, we found no similar published case.
We realize that the proposed situation is challenging, requiring a multidisciplinary anesthetic and neuro-ophthalmologic approach in which numerous factors must be evaluated. These include patient characteristics and general health (ie, a young pregnant woman is not the same case as an elderly man at high systemic risk), the type of surgery to be performed (urgent or not), the affected nerve, and the cause of palsy and its evolution (eg, microvascular ischemia, aneurysm, malignancy, giant cell arteritis).5
It is our belief that spinal anesthesia need not always be precluded in cases of preexisting ocular motor palsy. For example, spinal anesthesia may be appropriate in a case of ocular motor palsy of the third cranial nerve after 1 month's evolution in a diabetic and hypertensive patient older than 50 years who was previously diagnosed as having microvascular palsy; that is, in this case, carrying out spinal anesthesia does not seem to increase the risk of worsening the preexisting palsy or of contributing to other ocular motor problems.
In all cases, patients should be informed of the different anesthetic techniques that could be used in each situation, with disclosure of advantages and disadvantages, as no technique is risk-free. If subarachnoid anesthesia is selected as the best option, we believe it is appropriate to take preventive measures, such as subarachnoid puncture with a fine-gauge needle (ie, 27- or 29-gauge), supine positioning, and high liquid intake, in addition to thorough postoperative follow-up of palsy, in order to administer early treatment if warranted.
An epidural blood patch has not proven to be an effective treatment for ocular motor palsy after spinal puncture, and there is a risk of dural puncture.2 Some studies suggest that treatment with mannitol is an effective and safe option.2
In conclusion, the particulars of each case of ocular motor palsy must be considered prior to anesthesia, with patients fully informed of the potential risks and benefits of various techniques.