Paraclinoid aneurysms are defined as aneurysms originating from the clinoidal and ophthalmic segments of the ICA [1] and constitute between 5–14% of all intracranial aneurysms [4].
Clinoidal segment is the part of the ICA between the proximal and distal dural ring. It is the “interdural” segment of the ICA.
The aneurysms arising from this segment are classified into two types:
-
Anterolateral variant
-
Medial variant
The ophthalmic segment extends from the distal dural ring up to the origin of posterior communicating (PCom) artery. The ophthalmic and superior hypophyseal arteries (SHA) are the two major branches of the ophthalmic segment of the ICA.
The aneurysms arising from the ophthalmic segment are classified into three types:
-
Ophthalmic artery aneurysm: arises in close relation to the ophthalmic artery and projects superiorly.
-
Superior hypophyseal artery aneurysm: arises in relation to the superior hypophyseal artery and projects medially. They are further sub classified into parasellar and suprasellar variant.
-
Dorsal variant: arises from the dorsal aspect of the ICA slightly distal to ophthalmic artery [1].
As can be determined by studying the angiogram, the aneurysm in this case was the suprasellar variant of the superior hypophyseal artery aneurysm.
In addition to their characteristic features of SAH, the SHA aneurysms have a propensity to grow medially and to attain a large size causing compression of the optic pathway leading to visual field defects and their detection prior to rupture. Lower limb weakness and gyrus rectus hematomas in association with an aneurysmal SAH is most commonly seen with ruptured A Com aneurysms, and not SHA aneurysms. In this case, the aneurysm was long and was passing below the left optic nerve to emerge in the inter-optic space, leading to this unusual clinical presentation.
Endovascular treatment was not preferred in this case because of following reasons:
-
1.
Endovascular treatment does not relieve mass effect and even may lead to a larger size of aneurysm leading to pressure on the optic nerve with consequent visual field defects [5].
-
2.
The tortuosity of the ICA in this region makes coiling difficult.
-
3.
Coiling in this type of aneurysms is associated with a high rate of recurrence [6].
-
4.
Endovascular treatment is not available at present in the government hospital where the patient was treated, and also in many hospitals across the country. The endovascular treatment is very expensive in the private hospitals in our country and majority of the patients cannot afford the treatment cost. Hence, clipping still remains the most economical and cost effective modality to treat most ruptured aneurysms including paraclinoid aneurysms with no significant difference in outcome as compared to the very expensive coiling techniques [7].
However, newer endovascular techniques using flow diverters and pipeline embolisation device have shown promising results in terms of improvement of visual symptoms, obliteration rate, complications and recurrence and may play a greater role in future in treatment of paraclinoid aneurysms [8]. However, financial constraints and availability of infrastructure for coiling will continue to be a major hurdle for these endovascular techniques particularly in developing countries around the world.
Surgery, though effective, presents unique challenges.
Gaining proximal control requires exposing the carotid artery in the neck.
Adequate visualisation of the neck requires intricate drilling of the anterior clinoid and the optic roof (Fig. 5). The distal dural ring needs to be opened to adequately mobilise the carotid.
In this case, the dome was adherent to the undersurface of the frontal lobe. Hence, the frontal lobe was fully dissected off the chasm and the right optic nerve only after the aneurysm was secured at the neck.
Delaying the surgery till 10th day following the ictus resulted in resolution of the mono paresis and resulted in a more relaxed brain which helped in drilling of the clinoid. Majority of studies do not show any difference in the incidence of vasospasm and outcome in good grade patients when aneurysms are clipped in the interval of 4 to 10 days of ictus. However, our experience has shown that clipping the aneurysm in this interval leads to a higher incidence of post-op vasospasm and poor outcome [3]. Hence, we clip aneurysm in the first 3 days or after 10 days of the ictus.
