Imaging the hypoglossal nerve

Abstract

a b s t r a c tThe hypoglossal nerve is a pure motor nerve. It provides motor control to the intrinsic and extrinsic tongue muscles thus being essential for normal tongue movement and coordination. In order to design a useful imaging approach and a working differential diagnosis in cases of hypoglossal nerve damage one has to have a good knowledge of the normal anatomy of the nerve trunk and its main branches. A successful imaging evaluation to hypoglossal diseases always requires high resolution studies due to the small size of the structures being studied. MRI is the preferred modality to directly visualize the nerve, while CT is superior in displaying the bony anatomy of the neurovascular foramina of the skull base. Also, while CT is only able to detect nerve pathology by indirect signs, such as bony expansion of the hypoglossal canal, MRI is able to visualize directly the causative pathological process as in the case of small tumors, or infectious/inflammatory processes affecting the nerve. The easiest way to approach the study of the hypoglossal nerve is to divide it in its main segments: intra-axial, cisternal, skull base and extracranial segment, tailoring the imaging technique to each anatomical area while bearing in mind the main disease entities affecting each segment.

Biomechanical and Morphometric Evaluation of Occipital Condyle for Occipitocervical Segmental Fixation

“…Mean distance between the C0-C1 joint and floor of the hypoglossal canal in the sagittal plane was 12.8 ± 1.3 mm. The mean BMD was 0.35 ± 0.12 g/cm 2 .…”

“…The hypoglossal canal passes transversally through the bone in the lateral and forward direction just above the base of the condyle antero-laterally at an axial angle of 459and may be divided by a small bony spicule. 2) To avoid hypoglossal nerve injury during screw placement, the occipital condyle screw must be parallel to the hypoglossal canal and the C0-C1 transarticular screw must pass directly medially and anterior to the hypoglossal canal. 12) Although the basion and hypoglossal canal can be used for anatomic landmarks during screw placement, both structures are difficult to identify by radiography and the basion is located posterior to the anterior margin of occipital condyle and close to the hypoglossal canal.…”

Ultrasound of the Hypoglossal Nerve in the Neck: Visualization and Initial Clinical Experience with Patients

“…9 In the radiologic diagnostic work-up, a segmental imaging approach is advised. [19][20][21] The medullary, cisternal, and skull base segments can be well examined with the existing protocols of MR imaging and CT. In the carotid and submandibular spaces, these imaging modalities are also recommended, but the nerve itself is usually not depicted.…”

“…In the carotid and submandibular spaces, these imaging modalities are also recommended, but the nerve itself is usually not depicted. 19,20,22 We are not aware of any study of the feasibility of the direct visualization of the extracranial hypoglossal nerve, though ultrasound (US) has been increasingly used to visualize peripheral nerves to diagnose and localize pathologies affecting them.…”

Isolated hypoglossal nerve palsy: an unusual rare presentation in systemic lupus erythematosus

“…In the majority of cases, cranial neuropathies are either multiple or occur in association with deficits in the ascending and descending pathways. Isolated cranial neuropathy is very rare and only described in anecdotal case reports and small case series 3,5 . This is the second case report of SLE complicated with isolated HNP 4 .…”