Benign Enhancing Foramen Magnum Lesions: Clinical Report of a Newly Recognized Entity

Benign Enhancing Foramen Magnum Lesions

Benign enhancing foramen magnum lesions have been previously described as T2-hyperintense small, enhancing lesions located posterior to the intradural vertebral artery. We present the first case with pathologic correlation. These lesions are fibrotic nodules adhering to the spinal accessory nerve. While they can enlarge with time on subsequent examinations, on the basis of the imaging characteristics and location, they do not necessitate surgical resection.

Evidence for the Vascular Origin of Benign Enhancing Foramen Magnum Lesions via Intraoperative Photographs: Case Report and Review of the Literature

A small, benign enhancing lesion posterior to the intracranial vertebral artery at the foramen magnum is a recently described image-based entity and believed to represent varix or ganglion. We report on an individual who underwent surgery due to a hybrid neurofibroma/schwannoma of the trigeminal nerve and additionally presented a small gadolinium-enhancing lesion in the right spinal canal at the level of the craniocervical junction (CCJ). The intraoperative finding of this enhancing lesion most likely represents the lateral internal vertebral venous plexus which does not require follow up or surgical excision.

Posterior Skull Base Anatomy and Pathology

A posterior skull base lesion is an uncommon radiological finding that may be noted incidentally or during targeted imaging of patients with clinical symptoms attributable to the lesion. It may be inflammatory or neoplastic in etiology, or may simply be an anatomic variant or a "don't-touch" lesion that should not be misinterpreted as something more ominous. A systematic approach to the evaluation of the posterior skull base is therefore required in order to differentiate lesions requiring immediate attention from those requiring a less urgent course of action or none at all. This review will focus on the imaging features of pathologic conditions that are more commonly encountered in posterior skull base CT and MR examinations.

C1-2 cyst presenting with syringobulbia: a case report

Extradural atlantoaxial cysts are typically related to C1-2 degeneration. Intradural cysts may cause secondary syringobulbia depending on the size and cerebrospinal fluid flow obstruction. However, medullary syrinxes have not been previously described with extradural cysts. Treatment of symptomatic lesions involves surgical resection, often via a far-lateral approach, with consideration of fusion if C1-2 instability is present. We present a case of an extradural C1-2 cyst with intradural extension causing syringobulbia. Effective surgical resection was accomplished via a far-lateral, partial transcondylar approach without fusion. It is important to recognize that cysts of extradural origin may exhibit intradural extension and compress critical neurovascular structures.

Venous structures can mimic masses in the foramen magnum

Benign enhancing lesions at the foramen magnum is a recently described entity and believed to represent a varix or ganglion. These lesions are typically described as being single, located posterior to the intradural vertebral artery, and not attached to the dura. These 2 cases demonstrate previously undescribed variations in appearance of these lesions including contacting the posterior inferior cerebellar artery and lateral epidural plexus/dura, segmental dilatations, transverse and linear configuration, and visualization on an unenhanced CT head. These lesions most likely reflect bridging veins and are structures that clinicians should be aware of to avoid unnecessary follow-up or surgical intervention.

Evaluation of a high-signal lesion posterior to the intracranial vertebral artery using 3D balanced fast-field echo imaging

Previous reports have identified a small, benign, high-signal lesion (HSL) posterior to the intracranial vertebral artery and associated with the ipsilateral spinal accessory nerve (SAN) using 3D fluid-attenuated inversion recovery (3D FLAIR) imaging as an emerging new entity. To elucidate the relationship between HSLs and SAN, 76 patients with 86 HSLs were evaluated using 3D FLAIR and 3D balanced fast-field echo (3D bFFE imaging). All HSLs showed contact with ipsilateral SAN on both the sequences. 3D bFFE imaging clearly distinguished between the two structures unlike 3D FLAIR. Moreover, SAN was surrounded by HSLs on 3D bFFE images, which may be a characteristic of this entity.

Comparison of Three Methods Used for Estimating Area of Foramen Magnum

OBJECTIVE

To compare whether there are any differences between the 3 methods used for measure area of foramen magnum (FM) in skulls.

METHODS

The FMs of 150 skulls were examined. Antero-posterior diameter, transverse diameter were measured using by Vernier caliper. The area of the FM was calculated by using 2 different formulas as described previously by Radinsky and Teixeira.The authors also applied stereological assessment method for estimating the surface area of FMs. The area was calculated 3 times manually using stereological point grid system for each skull.The authors compared the mean surface area of FMs obtained from each of these 3 methods estimating surface area of FMs whether there were any significant differences in between their results.

RESULTS

The mean areas of the FMs estimated according to Teixeria formula, Radinsky formula, and Cavalieri stereological method were respectively as follows: 790.47 ± 99.86 mm, 783.66 ± 99.34 mm, and 748.06 ± 100.19 mm. The authors observed significant differences (P < 0.05) in between the mean surface areas of FMs obtained from each of these 3 methods used for estimating the area.

CONCLUSION

There were significant differences (P < 0.05) in between the mean surface areas of FMs obtained from each of these 3 methods used for estimating the area.