Fenestrated carotid axis at the carotid bifurcation and long inferior petrosal sinus, novel findings

Fenestrations of the cervical carotid arteries are extraordinarily rare variants, and no previous evidence of the carotid bifurcation (CB) fenestration was reported. Also, the inferior petrosal sinuses (IPSs) with extracranial segments of different lengths are rare. Fenestrations of the IPSs were not reported previously. Such novel morphologies are reported here. The anatomical variations described herein were detected during meticulous analysis of archived CT angiographic data obtained from a 45-year-old female subject. On the left side, variants of the carotid system were found: an 8.42 mm long fenestration was observed on the CB, extending from the common to the internal carotid artery, with unequal limbs. The superior thyroid artery originated from the CB. Also, a 5.55 cm long extracranial segment of the IPS was detected along the internal jugular vein (IJV). They both appeared as a high, parapharyngeal duplication of the IJV. The extracranial IPS had a 9.01 mm long fenestration. The IJV was compressed between the C1 transverse process and the digastric muscle. A partially ossified 2.24 long left styloid process was observed. Fenestrated CB and, respectively, extracranial IPS, are novel risk morphologies for surgeons and interventionists that should be acknowledged and documented preoperatively.