Keywords
AICA-PICA variant - intrameatal aneurysm - coiling
A 45-year-old woman presented with history of sudden-onset headache, recurrent vomiting, and mild imbalance on walking. There were no seizures, loss of consciousness, hearing impairment, tinnitus, facial weakness, neck manipulation, or head injury. On examination, the patient had tandem gait impairment. Subarachnoid hemorrhage (SAH) was seen on computed tomographic scan (CT) following which a digital subtraction angiogram (DSA), performed in other institute, revealed right anterior inferior cerebellar artery–posterior inferior cerebellar artery (AICA-PICA) variant with distal aneurysm ([Fig. 1A]). Normal configuration of AICA and PICA was seen on left with no evidence of any arteriovenous malformation or fistula distal to AICA-PICA common trunk. The patient was posted for surgery, with plan for occipital to AICA-PICA variant bypass, but aneurysm could not be located during exploration of the vessel. Repeat DSA with three-dimensional (3D) angiogram overlapped with Xper CT confirmed an aneurysm in intrameatal location of right AICA-PICA common trunk ([Figs. 1B and C], and [2]). Post exploration, the patient's headache worsened and developed intention tremors in the upper limb. Magnetic resonance imaging (MRI) showed edema with few lacunar infarcts in the right cerebellar hemisphere ([Fig. 1D, E]). The patient was now taken up for coiling with parent vessel occlusion. With 6F right femoral arterial access, a 6F Chaperone guiding catheter was negotiated into the left vertebral artery (VA). Echelon microcatheter over microwire was negotiated into the aneurysm, and after confirming location with microcatheter shoot, inside out coiling was done with multiple detachable platinum coils. Postcoiling angiogram showed exclusion of aneurysm from circulation and filling of the distal territory through collaterals ([Fig. 1F, G]). The patient had an uneventful recovery and was discharged 1 week later with mild residual intention tremor. At 3-month follow-up, the patient had no residual deficit.
Fig. 1 DSA showing right AICA-PICA variant with distal aneurysm. (A) CT brain showing SAH. Right VA angiogram (B) & 3D Angiogram overlapped to XPER CT (C) showing right AICA-PICA variant intrameatal aneurysm. Post surgical exploration MRI DWI (D) & ADC (E) images. Post embolization left VA angiogram arterial phase (F) and parenchymogram (G) are shown.
Fig. 2 Repeat DSA with 3D angiogram overlapped with Xper CT confirming an aneurysm in intrameatal location of right AICA-PICA common trunk.
Discussion
Distal AICA-PICA variant aneurysms are very rare with fewer than 10 cases reported till date.[1]
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[8] Intrameatal location for AICA aneurysms is also uncommon.[9] The AICA during its course has an abrupt turn at the internal auditory meatus and is in close relation to cranial nerve VII and VIII at that point. Common AICA-PICA trunk has similar course as that of AICA with the vessel dividing in rostral and caudal division. The caudal division reaches inferior surface of cerebellum and then takes over the territory of PICA.[3] The vessel is in close proximity to cranial nerve VII and VIII in the loop at internal auditory meatus, and thus facial paresis or hearing impairment with or without tinnitus can be part of initial presentation of the aneurysm or complication of surgery. As intrameatal location is not a branching point, the possible etiology for aneurysm might be dissection or hemodynamic stress due to accentuated turn in the vessel.[7] Surgical management of distal AICA or AICA-PICA variant aneurysms and intrameatal aneurysms has been proposed as first-line management due to concerns regarding catheter navigation and possible adverse effects of parent vessel occlusion.[7]
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[11] An occipital to AICA bypass has also been proposed as part of management plan.[1]
Surgical management has high chances for postoperative morbidity due to deep location of aneurysm, proximity of important neurological structures to the aneurysm, and lack of expertise due to rarity of such aneurysms. Successful endovascular management of proximal AICA aneurysms has been reported previously.[7] Only one AICA-PICA variant has been reported to be successfully managed endovascularly, but the patient had already sustained a cerebellar infarct.[1] The outcome of this case suggests that endovascular management can help in successful management, with lesser complications, and it should be tried in distal AICA or AICA-PICA aneurysms and those in intrameatal locations. Preprocedure balloon test occlusion may help assess the possible postprocedure morbidity.
Author Contributions
Vikram Huded: Drafting the manuscript, study concept, supervision, and coordination.
Vikram Bohra: Drafting the manuscript, study design, literature search, interpretation of data, and acquisition of data. Romnesh DeSouza: Literature search, interpretation of data, and acquisition of data.
Disclosures
None.
