Keisuke Hatano1, Hiroki Ohashi2, Daichi Kawamura2, Akira Isoshima2,3, Hiroyasu Nagashima2,4, Satoru Tochigi2,5, So Ohashi2,6, Jun Takei2, Akihiko Teshigawara2,5, Satoshi Tani2, Yuichi Murayama2, Toshiaki Abe2,7. 1. Department of Neurosurgery, The Jikei University School of Medicine, 3-25-8 Nishishinbashi, Minato-ku, Tokyo, 105-8461, Japan. hatakenosuke@gmail.com. 2. Department of Neurosurgery, The Jikei University School of Medicine, 3-25-8 Nishishinbashi, Minato-ku, Tokyo, 105-8461, Japan. 3. Department of Neurosurgery, Omori Red Cross Hospital, 4-30-1 Chuo, Ota-ku, Tokyo, 143-8527, Japan. 4. Department of Neurosurgery, The Jikei University Katsushika Medical Center, 6-41-2 Aoto, Katsushika-ku, Tokyo, 125-8506, Japan. 5. Department of Neurosurgery, The Jikei University Kashiwa Hospital, 163-1 Kashiwashita, Kashiwa-shi, Chiba, 277-8567, Japan. 6. Department of Neurosurgery, Kawasaki Saiwai Hospital, 31-27 Omiyacho, Kawasaki-shi Saiwai-ku, Kanagawa, 212-0014, Japan. 7. Department of Neurosurgery, Mishima Central Hospital, 1-3 Midoricho, Mishima-shi, Shizuoka, 411-0848, Japan.
Abstract
BACKGROUND: It is important to distinguish foramen magnum arachnoiditis (FMA) from Chiari malformation (CM) before surgery because the operative strategies for these diseases differ. In the current study, we compared pretreatment magnetic resonance imaging (MRI) of FMA with CM and investigated the MRI findings useful to differentiate between these diseases. METHODS: We retrospectively reviewed patients with FMA or CM aged ≥ 18 years who underwent surgeries at our institution between 2007 and 2019. The morphologies of the syrinx, neural elements, and posterior cranial fossa were preoperatively evaluated with MRI. We used the receiver operating characteristic (ROC) curve for the fourth ventricle-to-syrinx distance (FVSD). RESULTS: Ten patients with FMAs and 179 with CMs were included. FVSD in the FMA group was significantly shorter than that in the CM group (7.5 mm [IQR, 2.8-10 mm] in FMA vs. 29.9 mm [IQR, 16.3-52.9 mm] in CM, p < 0.0001). The other MRI findings that showed the height, size, and length of the syrinx; size of the foramen magnum; degree of cerebellar tonsillar descent; shape of the cerebellar tonsil; and dorsal subarachnoid space at the foramen magnum differed significantly between the two groups. The ROC curve analysis showed that patients whose FVSD was less than 11 mm could be diagnosed with FMA with a specificity of 90% and sensitivity of 96%. CONCLUSIONS: A more cranial syrinx development (FVSD < 11 mm) appears to be the characteristic MRI finding in FMA.
BACKGROUND: It is important to distinguish foramen magnum arachnoiditis (FMA) from Chiari malformation (CM) before surgery because the operative strategies for these diseases differ. In the current study, we compared pretreatment magnetic resonance imaging (MRI) of FMA with CM and investigated the MRI findings useful to differentiate between these diseases. METHODS: We retrospectively reviewed patients with FMA or CM aged ≥ 18 years who underwent surgeries at our institution between 2007 and 2019. The morphologies of the syrinx, neural elements, and posterior cranial fossa were preoperatively evaluated with MRI. We used the receiver operating characteristic (ROC) curve for the fourth ventricle-to-syrinx distance (FVSD). RESULTS: Ten patients with FMAs and 179 with CMs were included. FVSD in the FMA group was significantly shorter than that in the CM group (7.5 mm [IQR, 2.8-10 mm] in FMA vs. 29.9 mm [IQR, 16.3-52.9 mm] in CM, p < 0.0001). The other MRI findings that showed the height, size, and length of the syrinx; size of the foramen magnum; degree of cerebellar tonsillar descent; shape of the cerebellar tonsil; and dorsal subarachnoid space at the foramen magnum differed significantly between the two groups. The ROC curve analysis showed that patients whose FVSD was less than 11 mm could be diagnosed with FMA with a specificity of 90% and sensitivity of 96%. CONCLUSIONS: A more cranial syrinx development (FVSD < 11 mm) appears to be the characteristic MRI finding in FMA.
Entities:
Keywords:
Chiari malformation; Foramen magnum arachnoiditis; Magnetic resonance imaging; Syringomyelia