Type I split cord malformation with an usual bony morphology.

Variations in the configuration of the bony septum found in patients with split cord malformations are rare. We report the seemingly rare occurrence of a midline bony septum that ended posteriorly as a fully formed bony spinous process. We speculate that this variation is due to misplaced mesodermal cells associated with the primitive endomesenchymal tract during approximately the third week of foetal life. The clinician that manages these patients may wish to consider this rare morphology and avoid excessive manipulation of such a process, which could potentially injure an underlying hemicord.

Retrosplenic course of the transverse cervical artery with the suprascapular artery travelling through the suprascapular notch.

Anatomical variations of the transverse cervical and suprascapular arteries are common. We report an adult male cadaver found to harbour an unusual variation of the right course of these two arteries. The transverse cervical artery arose independently from the first segment of the subclavian artery and passed deep to the anterior scalene muscle, a course which, to our knowledge, has not been reported before. Simultaneously, the ipsilateral suprascapular artery arose from the third segment of the subclavian artery and travelled posteriorly with the suprascapular nerve deep to the suprascapular ligament. We believe this is the first report of such a simultaneous occurrence.

A complex dural-venous variation in the posterior cranial fossa: a triplicate falx cerebelli and an aberrant venous sinus.

Variations of the dural folds and the dural venous sinuses are seldom reported in the extant medical literature. Such variations in the posterior cranial fossa may be problematic in various diagnostic and operative procedures of this region. We report our observation of an extremely rare variation of the falx cerebelli and posterior cranial fossa venous sinuses encountered upon dissection of a young male cadaver. In this specimen the falx cerebelli was duplicated with dimensions of 45.3x5.1 mm and 49.8x5.3 mm for the right and left falces respectively. The distance between the two falces was 3.2, 4.5 and 7.8 mm at their proximal, middle and distal thirds. An accessory small falx (31.8x2 mm) was also found approximately 3.4 mm lateral to the right falx cerebelli and blended with the lateral surface of the right falx cerebelli. There was only one occipital venous sinus (diameter, 2.5 mm) and no marginal sinus was detected. At the right floor of the posterior cranial fossa (posterolateral to the foramen magnum) an additional dural venous sinus was found, which connected the terminal portion of the right sigmoid sinus to the occipital and right transverse sinuses via one medial and two lateral branches respectively. We believe that such a complex dural-venous variation in the posterior cranial fossa has not previously been reported. Neurosurgeons and neuroradiologists should be aware of such variations, as these could be potential sources of haemorrhage during suboccipital approaches or may lead to erroneous interpretations of imaging of the posterior cranial fossa.

A rare variation of the posterior cranial fossa: duplicated falx cerebelli, occipital venous sinus, and internal occipital crest.

Folds of the meningeal layer of the dura mater, the falx cerebri and tentorium cerebelli, traverse the vertebrate intracranial cavity and thus compartmentalise the brain. The falx cerebelli, another dural fold, is found in the posterior cranial fossa and attaches to the inferior aspect of the tentorium cerebelli and to the internal occipital crest. We present a case of a duplicated falx cerebelli, occipital venous sinus and internal occipital crest that was detected upon routine dissection of a male cadaver. Since haemorrhage of a dural venous sinus can be a fatal complication of posterior cranial fossa surgery, knowledge of venous sinus variations in this region may prevent unpredictable complications during intracranial procedures.

A rare variation of the vertebral artery.

Variations of the vertebrobasilar arterial complex are important with regard to their potential clinical impact. We present an unusual case of the vertebral artery, in which the left vertebral artery in its ascent in the neck through the transverse foramina passed posteriorly between the transverse processes of C3 and C4 and supplied the posterior muscles of the neck without continuing intracranially. Albeit speculatively, we hypothesise that the variation of the vertebral artery reported here was caused by degeneration of the proximal portion of the left postcostal longitudinal anastomosis (i.e. C1 and C2 intersegmental arteries) in the context of a persistent third cervical intersegmental artery. Our case is unique in that the left vertebral artery terminated extracranially. Knowledge of the variations of the vertebrobasilar arterial complex is important for surgeons operating at the skull base, craniocervical junction, and cervical region, and for clinicians interpreting the imaging of this region.

A rare variation of the inferior alveolar artery with potential clinical consequences.

Variations of the inferior alveolar artery are seemingly quite rare, especially with regard to its origin from the maxillary artery. We present an unusual case of an inferior alveolar artery that originated from the external carotid artery. To the best of our knowledge, our case is one of only two reports of the inferior alveolar artery arising from the external carotid artery. The clinician who deals with the mandibular region should be aware of such a variation in the arterial architecture.