Dear editor,
Atlas (C1) hypoplasia is a rare cause of occipital headache (1). Presented herein are three patients with C1 hypoplasia who were diagnosed with an occipital headache.
Patient 1: A 30-year-old male patient presented with numbness in the right arm and headache radiating to the neck for 8 years. The patient had hypoesthesia in the C4-T1 dermatome of the right upper extremity, and deep tendon reflexes were bilaterally hyperactive. The cervical computed tomography (CT) imaging revealed an 11 mm anteroposterior diameter of the spinal canal at the C1 level. The sagittal magnetic resonance imaging (MRI) revealed a spinal canal diameter of 8 mm. T2-weighted MRI showed hyperintense areas consistent with myelopathy in the cord at the C1 level. The preoperative visual analog scale (VAS) score was 9. Post-operative headache was completely resolved (Table 1).
Patient 2: A 31-year-old female patient was admitted with complaints of headache radiating to the neck and right hemicranial numbness for 10 years. Neurological examination was normal. The cervical CT revealed a 9 mm anterior-posterior diameter of the spinal canal at the C1 level. The sagittal MRI revealed an 8 mm anteroposterior diameter of the spinal canal. T2-weighted MRI showed hyperintense areas in the cord at the C1 level (Figure 1, 2). The preoperative VAS score was 9. The postoperative headache was completely resolved (Table1).
Patient 3: A 42-year-old female patient presented with complaints of headache radiating to the neck and numbness in the arms for 15 years. Neurological examination was normal. The cervical CT revealed an 11 mm anteroposterior diameter of the spinal canal at the C1 level and 9 mm in the sagittal MR, without myelopathy. The preoperative VAS score was 7. The postoperative 3rd-month VAS score was 1 (Table 1).
Occipital headache accounts for 15-20% of all chronic and recurrent headaches (2). The source of pain is often the C1–C3 spinal nerves, C0-C3 intervertebral joints, dura mater, or bone structures (3). However, its symptoms and clinical overlap with other headache forms lead to difficulties in diagnosis and to misdiagnosis in ~50% of the patients (1).
C1 hypoplasia is a rare condition that causes spinal stenosis, myelopathy, and occipital headache. C1 has three ossification centers originating from the rostral part of the first sclerotome (1). These three primary ossification centers are rarely far enough from each other (4). This causes hypoplasia and narrowing of the canal diameter.
The normal sagittal spinal canal diameter is 16-25 mm at the C1 level. Spinal stenosis is considered when the canal diameter is <14 mm. A canal diameter of 10 mm or less in patients poses a risk in the myelopathy clinical manifestation development (5). In most patients, the diagnosis is delayed because the narrowing does not cause serious neurological findings for a long time. The literature reported that posterior arch removal of the C1 lamina and decompression is effective in the regression of symptoms caused by C1 hypoplasia (1). In our three patients, clinical symptoms significantly improved after removal of the C1 posterior arch and atlantooccipital membrane.
In conclusion, patients with occipital headaches, which are resistant to medical therapy, should be evaluated for C1 hypoplasia. Patients should be considered as a whole while examining the radiological images, and the craniocervical junction should not be ignored. Surgical removal of the C1 posterior arch, atlantooccipital membrane, and surrounding degenerative ligaments with a posterior approach and stenosis relief is a safe and effective treatment method for occipital headache.