Clipping vs coiling of posterior communicating artery aneurysms with third nerve palsy

Treatment of third nerve palsy (TNP) from posterior communicating artery (PComA) aneurysms traditionally involves microsurgical clipping of the aneurysm.^1–3 More recently, embolization with Guglielmi detachable coils (GDCs) has been advocated as an alternative treatment of aneurysms and is accepted as effective and safe for decompressing the mass effects on cranial nerves.^4–7 We questioned whether coil embolization might result in complete decompression of mass effect because of the proximity of the aneurysmal sac to third nerve. On the other hand, microsurgical clipping might result in a better outcome of TNP due to disconnection of clipped aneurysm with the third nerve and complete decompression of mass effect.

Therefore, we reviewed our single-center experience over the past 5 years to determine whether surgical clipping or an endovascular procedure is better to treat PComA aneurysm with TNP. In addition, we assessed the factors attributed to the prognosis of TNP in each treatment.

Methods.

Between 2000 and 2004, 17 patients with PComA aneurysm had TNP as their presenting symptoms. None of the patients included in this study had a history of subarachnoid hemorrhage. All patients were women, with a mean age of 52.6 ± 13.0 years (range 29 to 75). The medical records of these patients were reviewed for clinical data and confirmation of aneurysm size and direction. Patient age, smoking, other microvascular risk factors (diabetes mellitus and hypertension), duration of TNP before treatment, and degree of TNP at admission were noted.

Ten of the 17 patients (58.8%) underwent endovascular coiling, and complete aneurysm closure was achieved. Seven of 17 patients (41.2%) underwent microsurgical clipping. The sac of the aneurysm was opened after clipping to free the third cranial nerve in two surgical patients. In five patients, the aneurysm adhered to the third nerve, and the dome was divided rather than dissected from the nerve to avoid nerve injury.

To identify multiple factors that would predict complete recovery of TNP, we analyzed categorical variables by the Fisher’s exact test. Comparisons between complete and incomplete patient group were made using the Mann–Whitney U test for continuous variables. All values are expressed as mean ± SD or frequency and percent where appropriate. Differences were considered significant at p < 0.05.

Results.

Follow-up data were available for all 17 patients, for periods ranging from 4 to 40 months (mean 17.6 ± 10.9). Complete resolution in nine patients (52.9%), incomplete resolution in seven (41.2%), and no change in one (5.9%) were observed. The recovery of third nerve started with the levator palpebrae muscle and was followed by the medial rectus muscle. Upgaze (superior rectus muscle) or downgaze (inferior rectus muscle) was mostly noted in incomplete recovery patients. Mild ptosis of 1 to 2 mm, compared with the contralateral eye, persisted for all patients, but this did not cause any clinical disability. All patients exhibited a sluggish direct reaction to light in the affected pupil. There was no statistical difference in complete TNP recovery as opposed to incomplete recovery with both treatment modalities (table). Both techniques are thought to be of clinical benefit for the management of PComA aneurysms with TNP.

Discussion.

Impairment of third nerve function has been attributed to the direct compressive effect of an enlarging aneurysmal sac within the suprasellar cistern and to the irritant effect of an adherent aneurysm.^2,8 The surgical clipping of aneurysms causing third nerve symptoms is known to be effective in relieving mass effect.^1–3 Published data revealed that 62 to 90% of patients with TNP showed complete cranial nerve recovery by early surgical clipping within 2 weeks from symptom onset.^1–3 Similar results have been reported in endovascular coiling.^4–7 Unlike surgical clipping, endovascular treatment does not immediately resolve the mass effect of an aneurysm; the loss or reduction of aneurysmal pulsatility afforded by coils embolization may, however, be more important in the resolution of TNP caused by cerebral aneurysms than in anatomic detachment of the third nerve from an adjacent and adherent cerebral aneurysm by surgical clipping. In our results, there was no statistical difference in outcome between endovascular and neurosurgical treatment. Although mass effect remains after endovascular packing, TNP improves comparably to the recovery observed after surgical clipping. These data provide evidence that, at least for aneurysm-compressive cranial neuropathy, GDC embolization may be clinically beneficial. A large-scale randomized study will be needed to verify equivalence or detect a difference in the benefits of these two techniques.

Previous small studies of outcomes after treatment reported that timely surgery for the aneurysm was associated with a more complete recovery of TNP.^8,9 There was a correlation between degree of oculomotor nerve recovery and mean time to therapeutic intervention. Age, sex, interval between onset of retrobulbar pain and TNP, size, and location were unrelated to oculomotor nerve recovery.⁹ Contrary to previous reports, older age and the presence of microvascular risk factors (smoking, diabetes mellitus, and hypertension) might decrease the chances of complete TNP recovery.⁷ In present study, the presence of diabetes, older age, delayed intervention, and complete TNP at presentation were poor prognosticators of complete recovery in the coiling group. In the microsurgical clipping group, patient age was the only significant factor for recovery of TNP. Other factors, such as the presence of hypertension, aneurysm size, history of smoking, and treatment modalities, were not indicative of recovery of neural function in our series. Our results showed that older patients who had risk factors for microvascular cranial nerve palsy were least likely to have complete recovery regardless of treatment modalities. The vascular supply to the cranial nerve that is partially compromised by diabetes, hypertension, or atherosclerosis may not be the optimal milieu for regeneration.