【はじめに】前方に発生した神経鞘腫の1例を経験したので報告する．【症例】70歳男性で右肩甲部から上腕にかけての強い疼痛，しびれ感と右上肢の筋力低下および軽度歩行障害を主訴に平成18年1月23日初診した．MRIで大頭孔から環椎にいたる脊髄右側前方にT1強調で低信号，T2強調で高信号を呈しGdで造影された腫瘍をみとめた．2月7日lateral approachで手術を施行した．右側の後頭顆，環椎後弓，軸椎椎弓を片側切除し硬膜を切開して腫瘍を摘出した．病理組織は神経鞘腫であった．頚髄症JOA scoreは術前7点が術後5ヵ月で13.5点に改善した．腫瘍の再発はない．【考察】本症例のように前方にある腫瘍に対してlateral approachは比較的広い視野で摘出でき有用であると思われた．

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Paralysis of the ipsilateral arm and contralateral leg was first described by Wallenberg in 1901 as “hemiplegia cruciata”. At the level of upper cervical spinal cord, the fibers for upper limp and lower limb cross the midline at the different levels. Hemiplegia cruciata is produced by involvement of the crossed arm and uncrossed leg fibers of the pyramidal tract at the level of the decussation of the pyramid.
Etiology has been reported to be hemorrhage, occlusion of the anterior spinal artery and trauma such as fracture of the odontoid process, but hardly due to spinal cord tumor. It has been said that extramedullary tumor at this level is very difficult to be diagnosed because of varied and strange symptoms. So early diagnosis is important to understand the anatomy of this level.

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There are many reports on the malformation of the bone around the Foramen magnum. We have recently observed a patient who came our hospital with a main complain of strain of the neck and an unsteady walking.
This patient showed short neck, low hair line, moving pain at the neck and a restricted movement and showed an Atlas occipitalisation by roentgenography and was diagnosed as a Basilar Impression.

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There are a few reports about surgery of foramen magnum tumors by the anterior approach. We report a case of foramen magnum meningioma who was treated by transoral extirpation and had a good result. A 77-year-old woman was admitted to the Kumamoto University Hospital on June 9th, 1988. 10 year prior to the admission she noticed the numbness in the hands and legs. In 1984 she suffered from pain and dysesthesia in the right chest. In May 1988 she could not walk at all. MRI disclosed an intradural and extramedullary tumor at the level of foramen magnum. The tumor was resected completely by transoral approach and a posterior occipito-C2 fusion by Luque rectangular rod was added. After the operation her pain in the right chest faded away and muscle strength improved gradually. Five months after the operation she is doing standing exercise.

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Five patients with vertigo were examined radiologically and neurotologically.
Generally a posterior inferior cerebellar artery (PI-CA) branching from the vertebral artery (VA) below the foramen magnum is seldom seen in normal persons. But if a PICA or bypass branches from the VA below the foramen magnum, vertebro-basilar insufficiency may occur due to pressure on the bloodstream from the edge of the foramen magnum, especially during tests in the hanging head position.
The diagnosis of vertebro-basilar insufficiency induced by pressure by the edge of foramen magnum was made by vertebral angiography in five cases.
Electronystagmography results also presented.

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A 48-year-old female complained of severe rotatory vertigo. Downward vertical nystagmus was observed when her head hung down. Magnetic resonance imaging (MRI) showed left cerebellar infarction and vertebral angiography (VAG) showed occlusion of the left posterior inferior cerebellar artery (PICA). A bypass branch from the left vertebral artery (VA) below the foramen magnum was seen on VAG. If there is a bypass branch from the VA below the foramen magnum, vertical nystagmus may occur because of pressure on the bloodvessel by the edge of the foramen magnum, especially when the head is hanging down.
VAG was more useful than MRI in demonst-rating the occlusion of PICA in this case. A definite diagnosis aid in the choice of medication, in general advice about life style, and also in psychological counseling.

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  Objective : Achondroplasia is the most common heritable skeletal dysplasia. Cervicomedullary compression at the foramen magnum is highly associated with severe neurological complications including sudden death. Distinguishing which patients are at a high risk of neurological compromise is difficult. The aim of this study is to clarify the radiological features of the foramen magnum in achondroplasia that requires surgical decompression.

  Materials and methods : We conducted a retrospective study at our department with regard to the radiological features of the foramen magnum in achondroplasia, including the sagittal diameters of the cervicomedullary junction, arachnoid space on magnetic resonance imaging (MRI), and the basion-opisthion interval on computed tomography (CT). We also measured the cross-sectional area of the cervicomedullary junction, arachnoid space on MRI, and foramen magnum on CT. Patients’ data were classified into operative and non-operative groups. From January 2012 to December 2015, nine children with achondroplasia were initially evaluated radiologically. The mean age at initial evaluation was 11.6 months, and the mean follow-up period was 33.1 months. Foramen magnum decompression was indicated for children with morphological change of the cervicomedullary junction under compression or intramedullary signal change on MRI.

  Results : Seven of nine patients underwent foramen magnum decompression. The remaining two were managed conservatively. In the operative group, we found smaller sagittal diameter of the cervicomedullary junction and arachnoid space on MRI, but were not statistically significant (p=0.0556 and 0.0556, respectively). Besides, the operative group showed smaller cross-sectional area of the foramen magnum on CT, which was also insignificant statistically (p=0.0556). The morphological comparison of the foramen magnum on CT showed insufficient expansion of the posterior margin on the operative group. This anatomical feature caused ventral projection and dorsal compression to the cervicomedullary junction.

  Conclusions : The smaller size of the foramen magnum in children with achondroplasia can be related to cervicomedullary signal change or compressive deformity on MRI. Further study is necessary to establish the surgical criteria for foramen magnum decompression in children with achondroplasia.

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Foramen magnum tumors produce many bizarre symptoms, and several reports have mentioned the pitfalls in diagnosing such tumors. In this report, we confirm such a tumor causing motor disturbance of the contralateral extremities. A 64-year-old male with a 2-year history of numbness of the right extremities and motor disturbance of the left extremities presented to our hospital. Neurological findings were as follows: hypoesthesia of the right hand and both lower legs, weakness of the left extremities, hyperactive deep tendon reflexes in the left upper and lower extremities, and Hoffmann's and Babinski's signs on the left side were present. On MR images, myelogram and CT-myelogram a dumbbell shaped tumor, which showed compression of the cervical spinal cord from the right side at the level of C1-C2, was noted. The tumor was surgically resected, and on histological examination it was diagnosed as a neurinoma. In this case the tumor was situated at C1-C2 below decussation, however, weakness and increased deep tendon reflexes were found in the contralateral extremities. The main function of the upper cervical spine is rotation. The spinal cord is compressed by contralateral lamina during rotational motion of the upper cervical spine. Thus, as noted in the present study, contralateral motor disturbance may occur.

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We report three cases of anomalies of the craniovertebral junction with myelopathy. Case 1 was a 28-year-old man who complained of muscle weakness of his right upper limb and gait disturbance. He was diagnosed as having basilar impression, atlantoaxial dislocation and hyperplasia of the dens with spondyloepiphyseal dysplasia. Case 2 was a 15-year-old woman who complained of gait disturbance. She was diagnosed as having ossiculum terminal and atlanto-axial dislocation with Down's Syndrome. Case 3 was a 67-year-old man who complained of limb numbness and gait disturbance. He was diagnosed as having atlanto-occipital fusion, basilar impression and atlanto-axial dislocation with spongilosis. All patients had surgical treatment with improvement in their cord symptoms.

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Tumors of the magnum are rare with many of these lesions having curious presentations due to the complex anatomy of this region there by making their diagnosis difficult.
During the last 12 years, we have encountered 6 cases of foramen magnum tumors, all of which were extramedullary, 4 neurilemomas, one meningioma and one neurofibroma.
All cases were treated with surgical excision. There were no deteriorations in these cases after surgery. From the foramen magnum to C2 level, the cervical canal is wide, so if a space occupying lesion is here, the symptoms are often very slight, although the tumor may be relatively big. It is important to consider this tumor and to make an early diagnosis, MRI is very useful for this, and take appropriate treatment measures before permanent damage results.

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A 44-year-old female with foramen magnum menigioma was discussed which was clearly revealed by preoperative contrast enhanuced CT. This technique was very helpful to determine extirpation procedure or detect postoperative recurrence. Its availability should be stressed.

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軟骨無形成症の2小児例を経験した.症例1:2歳,男児.MRIで部狭窄,脊髄空洞症を合併したキアリI型奇形が指摘され,減圧術,CIの椎弓切除を施行した.術後の経過は順調で,歩行障害は改善した.症例2:1歳,男児.MRIで狭窄による延髄の圧迫を認め,減圧術を施行した.術後,合併していた肺高血圧は改善し,呼吸機能は改善していたが,1年11ヵ月後に肺炎を併発し死亡した.軟骨無形成症は頭蓋頸椎移行部の狭窄を高率に合併し,乳幼児例では呼吸障害を併発し,致死的になることがある.症状が軽微でも,頭蓋頸椎移行部に高度狭窄がみられる患児では,手術的治療を考慮すべきである.

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脊髄空洞症を合併したChiari奇形に対し,硬膜外層のみの減張切開による減圧術とC1 laminectomyを施行した.術後,いったん改善した神経症状が再度出現し,それに伴い縮小したSyrinxが増大した症例を経験した.その機序は今後の検討課題であるが,MRIでその変化を捉えられたことは意義のあることと思われた.

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Treatment for tumors located at the craniocervical junction is challenging because of their variety and the consequent difficulty of selecting the optimal surgical approach. We studied the long-term follow-up results of surgical treatment. <Materials and methods> Between 1984 and 2000, we treated 24 patients with tumors located at the craniocervical junction; seven meningiomas, five chordomas, four schwannomas, two neurofibromas, and six others. Age range was from 1 to 77 years old (average, 44). Surgical approaches consisted of the far lateral-transcondylar approach for six patients, the transoral approach for four, the transmaxillary approach for one, the transcervical approach for one, the frontobasal approach for two and laminectomy or the suboccipital approach for ten. Cranio-cervical fixation was performed for four patients. The mean follow-up period was 7.3 years. <Results> Total removal was performed for 17 patients and subtotal removal for seven. All meningiomas and schwannomas were totally removed and there was no recurrence. No surgical mortality was experienced. One case of CSF leakage after transoral removal of a foramen magnum meningioma and three cases of swallowing disturbance after removal of a meningioma, a metastatic tumor and an intramedullary hemangio-blastoma were encountered. Craniocervical fixation was successful for all patients. At the last follow-up, 15 patients had survived without recurrence, four had locally controlled tumors, and five patients had died. <Conclusion> Total removal of meningiomas and schwannomas at the cranio-cervical junction should be attempted at the first operation. Postoperative craniocervical stability is an important factor in the treatment of metastatic tumors, chordomas and neurofibromas invading bony structures.

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軟骨無形成症は構造的な鼻咽腔狭窄に加え，中枢性の睡眠時無呼吸も合併しやすいことから上気道手術を行っても睡眠時無呼吸症が改善されない例がある．今回，われわれは国立成育医療研究センターに軟骨無形成症で受診した47例のうち，睡眠時無呼吸症の疑いで耳鼻咽喉科に受診し上気道手術（アデノイド切除術・口蓋扁桃摘出術）を施行した10症例を対象に検討を行った．再手術例を併せると10例中7例（70.0％）は上気道手術により睡眠時無呼吸症状は改善し再燃もしなかったが，10例中3例（30.0％）はCPAPなどの保存的治療が必要であった．軟骨無形成症に伴う睡眠時無呼吸には閉塞性のみではなく，中枢性の睡眠時無呼吸や下気道疾患，低身長に対して行う成長ホルモン補充療法が複数の因子として影響していることが示唆された．

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