32.2.1 Vision Loss

Many suprasellar tumors, such as macroadenomas or craniopharyngiomas or even large chordomas, may present with occult but significant vision loss. Children are often not cooperative for reliable formal visual field testing. Simple threat testing or visual stimulus in all fields of vision can be used to detect significant deficits. Any patient with clinical or radiographic evidence of significant visual apparatus compromise should be closely monitored to avoid perioperative hypotension, which can result in hypoperfusion and can be devastating, even if transient. Weight-based corticosteroids can be used liberally in these cases as well.

One advantage of endonasal surgery, especially using an endoscope, is the ability to identify and preserve the subchiasmatic perforators from the superior hypophyseal arteries. Their anatomy should be closely studied by any surgeon operating in this region and branches identified and preserved intraoperatively. ³ This can be especially challenging for tumors such as craniopharyngiomas, which may receive partial supply from an occasional branch.

32.2.2 Cranial Nerve Injury

Avoidance of cranial nerve (CN) injury is a primary goal of any skull base surgery. Endonasal approaches were developed in large part to provide a corridor within the confines of the CNs, thus avoiding manipulation and injury. This advantage has been demonstrated in case series for many different tumor types. ^{4 ,​ 5 ,​ 6 ,​ 7} The abducens nerve, however, remains at high risk given its ventral origin (at the vertebrobasilar junction), long course, fragility, and frequent involvement with tumors that are ideal for EESBS (e.g., chordomas). It is particularly susceptible to injury at Dorello’s canal, where the nerve is interdural. Monitoring of CNs with electromyography can help localize them at the margin of the tumor and prevent injury. ^{8 ,​ 9 ,​ 10} Establishing a threshold for stimulation also provides prognostic information for recovery when there has been manipulation of the nerve.

32.2.3 Vascular Injury

Vascular injury is the most potentially devastating complication of any skull base surgery, but concern over vascular control adds a degree of fear to this complication with EESBS. However, the options for vascular control are the same as with “open” surgery, with the exception of suturing. The two-surgeon, four-hand technique becomes most critical during management of any vascular injury. This is especially critical for maintenance of view, troubleshooting/problem solving, and applying technical maneuvers such as holding pressure while increasing exposure. Skull base tumors can contact or encase vessels, and management strategies are different for petrous or cavernous segments of the internal carotid artery (ICA) and intracranial contributions to the circle of Willis (▶ Fig. 32.1).

In the event of an ICA injury, control of hemorrhage with suction and tamponade with a cottonoid are the first steps. Rapid notification of the rest of the surgical team and anesthesia providers is critical for optimal patient management. Evaluation of the injury and potential for wider exposure, proximal and distal control, and repair options are all part of the dialogue between co-surgeons. Options for repair are somewhat limited due to the inability to reliably suture. ¹¹ Very small holes, such as perforator avulsions, can often be sealed with careful bipolar coagulation of the side wall with little or no stenosis of the artery. Well-visualized injuries can often be pinched off with an aneurysm clip, applied via a single-shaft clip applier, with potential preservation of flow. For larger injuries, or for any poorly controlled injury, packing with muscle tissue is a proven, reliable option. Muscle tissue can be obtained from the rectus abdominis, temporalis, sternocleidomastoid, quadriceps (fascia lata exposure), or even nasopharynx/rectus capitis muscles. Muscle should be crushed to flatten it and release calcium to augment hemostasis. Any time there is significant, repetitive compression or manipulation of the ICA, consideration should be given to anticoagulation. This can be counterintuitive in the setting of ICA injury, but would be standard for any planned arteriotomy.

ICA preservation should always be the goal of any repair, with sacrifice as a last resort. However, sacrifice is tolerated in most patients and, as a result, is preferable to uncontrolled hemorrhage.

Intracranial arterial injury can be equally devastating and difficult to control. Packing is not a good option in this setting, as it can lead to devastating intracranial hemorrhage, and controlled suction alone is frequently used to localize and control bleeding. Sidewall bipolar coagulation on a low setting can be used as a vessel preserving technique. Microaneurysm clips are another option. Bleeding from very small perforator injuries often stops with warm saline irrigation, which optimizes conditions for activation of the coagulation cascade. Occlusion of any intracranial artery should be avoided whenever possible, but communicating arteries may be sacrificed if necessary, often without consequence. Control of hemorrhage is always the primary goal, however, and other techniques, such as those mentioned above, or simple compression with cotton or other similar material should be attempted prior to coagulation or clip sacrifice. For example, posterior cerebral artery (PCA) injury during craniopharyngioma resection can be managed with sacrifice of the P1 segment if the patient has an adequate posterior communicating artery, but loss of thalamic perforators can be devastating.

Any time there is a risk of vascular injury, neurophysiologic monitoring should be employed. Simple SSEPs can provide critical information about the consequence of maneuvers, such as sacrifice, and help guide intraoperative decision-making, especially in the absence of preexisting balloon test occlusion (BTO).

Immediate angiographic follow-up is essential after any significant vascular injury. Unless the artery is easily and convincingly controlled during surgery, continued tumor dissection should generally be aborted in favor of angiographic evaluation. Stenosis, thrombus (which can embolize), and pseudoaneurysm can all require urgent treatment that is delayed by prolonged tumor resection. Most of these conditions have reasonable endovascular salvage, and urgent bypass is rarely a practical consideration. High-risk tumors, such as chordomas with significant ICA involvement, especially if recurrent or radiated, should be evaluated with preoperative BTO, often relying on neurophysiologic testing (SSEPs or TCD [transcranial Doppler]) combined with evaluation of filling time or venous transit times under anesthesia in younger, less cooperative children.

32.3.1 Cerebrospinal Fluid Leak

CSF leak is the most common complication following intradural EESBS. Vascularized reconstruction, primarily with the nasoseptal flap based on the posterior nasal branch of the sphenopalatine artery, is the definitive component of a multilayer reconstruction. CSF leak rates have declined dramatically and approach those of many open approaches with the use of this and other local intranasal flaps. ^{12 ,​ 13 ,​ 14 ,​ 15} CSF leak rates are higher in children than in adults for several reasons, including delayed nasal development, resulting in smaller flaps, poor compliance with packing and postoperative restrictions, and difficulties with postoperative assessment. ¹⁶ All of these are amplified in tumors such as clival or craniocervical junction chordomas, where large defects are at the limits of the flap, and CSF leak may present only as retropharyngeal drainage.

CSF leak should be evaluated and treated urgently. If available, beta-2 transferrin testing can be used to confirm the nature of clear drainage. CT scan can be used to assess for an increase in pneumocephalus. Any increase with serial postoperative scans is clear evidence of a fistula. Persistent drainage (nasal sprays should be stopped) should be assumed to be CSF and treated accordingly. Lumbar drainage is not recommended as the primary treatment, since it is not effective in the majority of cases and will delay definitive treatment and increase risk of meningitis. Rather, a CSF leak is treated with re-exploration at the soonest reasonable time (▶ Fig. 32.2).

Nasoseptal flap necrosis is a rare event but can have devastating consequences if not correctly diagnosed. ¹⁷ It presents approximately 2 weeks postoperatively with signs of meningitis and frequently a foul smell from the surgical site. Diagnosis is confirmed with MRI that shows lack of flap enhancement. Treatment includes lumbar puncture and/or drain, re-exploration, flap debridement, and coverage with additional vascularized tissue when possible. Intravenous antibiotics complete the treatment, and prognosis is good, with low risk of developing a delayed CSF leak.