Presentation

A 70-year-old Asian male, undergoing treatment for seropositive rheumatoid arthritis (RA) with methotrexate (16 mg/week), prednisone (2 mg every other day), and tacrolimus (3 mg/day), presented with a three-month history of neck pain, dysarthria, and dysphagia. Although his treatment options were limited due to an allergy to sulfasalazine and financial constraints, he was in remission with the treatment. Physical examination revealed no significant findings except for left hypoglossal nerve palsy, which manifested as atrophy of the left tongue musculature and deviation of the tongue toward the left side (Fig. 1C). Computed tomography of the cervical spine showed a widened atlantodental interval and vertical deviation of the axis (Fig. 1A). Additionally, the tip of the odontoid process was dislocated into the foramen magnum. Magnetic resonance imaging of the neck disclosed high-intensity areas in the C2 lesion, stenosis of the foramen magnum, and deformation of the dens (Fig. 1B). These findings were consistent with basilar impression, anterior and vertical atlantoaxial subluxation, and cervical myelopathy. After surgical fixation of the cervical spine, the neurological signs and symptoms were resolved (Fig. 1D). We concluded that basilar impression resulting from vertical atlantoaxial subluxation had compressed the left hypoglossal nerve on the surface of the brainstem, causing hypoglossal nerve palsy.

Fig. 1
figure 1

The sagittal view of the CT scan of the cervical spine reveals that the tip of the odontoid process (red arrow) dislocated into the foramen magnum (blue arrow) and a widened atlantodental interval between the anterior arch of C1 (triangle) and the odontoid process (red arrow) (A). The sagittal view of the MRI of the neck (T2-weighted imaging) demonstrates high signal intensity at the C2 lesion (red arrow), stenosis of the foramen magnum (blue arrow), and deformation of the dens(triangle) (B). Preoperative examination of the patient's tongue showed unilateral atrophy of the left tongue (red arrow) and deviation toward the left side (blue arrow) (C). Postoperative examination revealed complete resolution of the atrophy and deviation (D)

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Discussion

Basilar impression is a serious complication of RA in which the tip of the odontoid process migrates upward into the foramen magnum due to the weakening of the supporting connective tissue and bony structures [1]. Cervical spine involvement in RA presents with a range of neurological symptoms [2]. However, the optimal frequency for evaluations for atlantoaxial subluxation remains undetermined. It is noteworthy that this case presents with the isolated hypoglossal nerve palsy manifestation, without symptoms of cervical myelopathy. This underscores the importance of isolated hypoglossal nerve palsy as a sign of cervical spine involvement in RA.