Suspected Orbital Compartment Syndrome Leading to Visual Loss After Pterional Craniotomy
Background : Perioperative visual loss is a potentially devastating surgical complication. Its occurrence is exceedingly rare after nonocular surgery, but recent literature has explored several etiologies contributing to its development.
Case Presentation : We document a case of perioperative visual loss after a pterional craniotomy for the excision of a temporal meningioma in a 47-year-old woman with no significant medical history. The intraoperative course was uneventful, with a myocutaneous flap reflected anteriorly across the orbit. Postoperatively, the patient demonstrated a third cranial nerve palsy and an afferent pupillary defect, with visual loss that persisted > 3 months postsurgery. A diagnosis of central retinal artery occlusion secondary to intraoperative orbital compartment syndrome was considered the likely etiology. However, several alternate diagnoses could not be excluded.
Conclusions : Orbital compartment syndrome should be considered in neurosurgical patients presenting with postoperative ophthalmoplegia and central retinal artery occlusion. We recommend a multidisciplinary perioperative approach to reduce the incidence of perioperative visual loss and orbital compartment syndrome in patients undergoing pterional craniotomy.
On the morning of postoperative Day 1, the patient reported vision loss in her left eye, while her clinical examination revealed erythema and conjunctival chemosis with left eyelid swelling. The ophthalmologic evaluation was notable for a continued leftCN III palsy with intact lateral rectus and superior oblique function, a nonreactive and dilated left eye with 3+ afferent pupillary defect by reverse (light perception), pallor throughout, a flat cherry red macula with blurred disc margins, left upper eyelid edema, and 18 mm Hg intraocular pressure bilaterally (reference range, 8 to 21 mm Hg). Fundoscopic examination showed a clear vitreous without plaques or occlusions, no perivascular sheathing, and no retinal hemorrhages. CT angiography revealed small outpouchings at the superolateral aspect of the left and right cavernous carotid, consistent with atherosclerotic calcifications. An echocardiogram revealed a Valsalva-dependent patent foramen ovale, but a venous Doppler ultrasound yielded negative results.
Repeat MRI showed denervation of the left medial rectus and minimal left-sided proptosis. A 3-month ophthalmologic follow-up revealed a persistent CN III palsy, including an afferent pupillary defect, absence of light perception in her left eye, and continued ophthalmoplegia. Repeat examination showed a left-sided 4+ afferent pupillary defect unreactive to light, 4+ pallor surrounding the optic nerve, macular atrophy, sclerotic vessels, and 17 mm Hg intraocular pressure bilaterally. The eye had diffuse atrophy of the inner retina and significant patchy atrophy of the outer retinal components without neovascularization of the iris. Postoperative retinal imaging can be seen in Figure 3. Her vision loss persisted at this encounter and has continued through subsequent follow-up examinations.
Discussion
Perioperative visual loss is a rare surgical complication, with an estimated incidence of once in every 60,000 to 125,000 cases.9 The mechanism of injury is variable and dependent upon the type of surgical intervention, with cardiac and spine surgeries carrying the greatest risk.10,11 The injury often results in either CRAO or ION, which may result in visual loss.1-3 POVL can also occur in the aftermath of rapid changes in intracranial pressure during decompressive craniotomies, though the pathophysiology in such cases is not well understood.5
Among the myriad ways in which POVL can occur, neurosurgical cases carry the unique risk of direct cranial nerve injury. Such an insult can lead to vision loss via optic nerve damage or ophthalmoplegia if damage occurs to CN III, IV, or VI. This can occur during manipulation or resection, especially if the surgical approach involves the orbital cavity or the cavernous sinus. Though neither space was entered in this patient, direct injury cannot be ruled out as the etiology for either her vision loss or persistent ophthalmoplegia. An alternate causative scenario for both symptoms involve an impaired blood supply, with the vision loss potentially occurring secondary to CRAO and the ophthalmoplegia to an alternate cause of decreased blood flow. It is unclear which of these 2 conditions occurred first or if they occurred due to the same insult, but OCS could lead to both. Though it is a less common etiology for POVL, this patient’s presentation was similar to those in previously reported cases, and OCS was identified as the likely diagnosis.
OCS is precipitated by an elevated orbital pressure, which leads to ischemia of the retina and damage to orbital contents. Though associated with retrobulbar hemorrhage and orbital trauma, another proposed mechanism for OCS is extrinsic orbital compression, resulting in increased IOP and subsequent CRAO.10 A cherry red spot is visible on fundoscopy, as only the macula with its thin retinal layer will permit the choroidal vessels to be visualized. In a separate process, the relative increase in orbital pressure may lead to impaired perfusion or damage of CN III. However, a causative relationship between the 2 may be difficult to establish. Such an injury to the oculomotor nerve is demonstrated by impaired function of the inferior oblique, superior rectus, inferior rectus, and medial rectus muscles, which may persist even after the compressive symptoms of OCS have resolved.12 Other reported symptoms of OCS include erythema, ophthalmoplegia, conjunctival chemosis, ptosis, corneal abrasion, and eyelid edema.12-15
Alternate Diagnoses
OCS is a diagnosis of exclusion, and several alternate mechanisms were considered before identifying it as the likely etiology. The patient’s preoperative imaging demonstrated a stable enhancing mass involving the left great sphenoid wing and left cavernous sinus, with displacement of the left middle cerebral artery, left cavernous internal carotid artery, and left optic canal. Dissection and removal of this tumor could have compromised the arterial or venous blood supply to the orbit, thus causing ischemia to the retina and other ocular structures. CN III was manipulated during surgery, and it may have been inadvertently damaged during exposure or resection of the tumor.
