Spinal cord tumors

Japanese: 脊髄腫瘍

Concept: Spinal cord tumors are neoplasms that develop and spread within the spinal canal. They originate from the spinal cord and spinal nerves, arachnoid mater, dura mater, as well as the vertebrae and surrounding soft tissues. Statistics: The incidence of spinal cord and spinal tumors is estimated to be approximately 3 per 100,000 population.
Classification and frequency by site of origin Spinal cord tumors are classified into epidural and intradural tumors based on the site of origin, with the ratio being approximately 2:3. Metastatic tumors are typical of extradural tumors, while intradural tumors include extramedullary tumors and intramedullary tumors. Schwannomas and meningiomas are the most common extramedullary tumors, while ependymomas and astrocytomas are the most common intramedullary tumors (Table 15-14-4).
1) Epidural tumor:
Most cases are malignant tumors such as metastatic tumors and lymphomas, but chordomas occur frequently in the sacral region. In addition, some schwannoma tumors may exist both intradurally and extradurally, resulting in a dumbbell-shaped tumor.
2) Intradural extramedullary tumor:
Schwannomas occur almost equally at all spinal cord levels, are most common in people in their 30s to 50s, and there is little gender predilection. In neurofibromatosis type 2, schwannomas often occur multiple times in the spinal cord. In contrast, meningiomas tend to occur near the foramen magnum and in the thoracic vertebrae, and are more common in women in their 40s to 60s.
3) Intradural intramedullary tumor:
Astrocytomas occur most frequently in the cervical and cervicothoracic spinal cord, with peak incidence in children and people in their 20s. In cases under the age of 10, approximately 90% of intramedullary tumors are astrocytomas. The vast majority of pediatric cases are benign, but approximately 25% of adult cases are malignant (anaplastic astrocytoma, glioblastoma). Ependymoma is the most common intramedullary tumor in adults.
Clinical symptoms The initial symptom of spinal tumors is often pain, regardless of the location of the tumor. In the case of epidural metastasis of malignant tumors, back pain and radicular pain are followed by paralysis of both legs several days, or in some cases, several hours later. In contrast, symptoms of intradural tumors progress relatively slowly, and it is not uncommon for one to two years to pass between the onset of symptoms and diagnosis. Intradural extramedullary tumors are usually located unevenly within the spinal canal, so compression of the spinal cord occurs asymmetrically, resulting in Brown-Séquard syndrome. In other words, motor paralysis, deep sensation loss, and temperature and pain loss on the contralateral side are observed below the spinal cord level of the tumor on the same side as the lesion. On the other hand, in intradural intramedullary tumors, motor and sensory functions below the spinal cord level of the lesion are generally impaired, but temperature and pain sensation in the sacral region is preserved, resulting in sacral sparing.
Diagnosis: In principle, MRI is used to diagnose spinal tumors, but plain spinal X-rays and CT scans are useful for diagnosing bone changes associated with the presence of a tumor. In metastatic tumors, the tumor can be seen compressing or squeezing the spinal cord from the extradural space, but metastatic lesions are often seen in bone tissue such as the vertebrae. Both schwannomas and meningiomas are well enhanced, and the spinal cord is displaced by the tumor. Schwannomas extend along the course of the nerve root, sometimes extending to the extradural space, but the tumor is located on the lateral side of the spinal cord (Figure 15-14-8A). On the other hand, in meningiomas, tumors are found attached to the dura on the ventral or ventrolateral side of the spinal cord. In intradural intramedullary tumors, the spinal cord swells in a spindle shape due to the tumor. Ependymomas are depicted as lesions that are strongly enhanced almost in the center of the swollen spinal cord (Figure 15-14-8B), and are frequently associated with cysts at the upper and lower poles. In contrast, in astrocytomas, the tumor contrast effect varies considerably from case to case, and the margins of the lesions are less clear than in ependymomas.
Treatment and prognosis Treatments for epidural metastasis of malignant tumors include surgery, radiation therapy, and chemotherapy. Of these, radiation therapy is highly effective and is the primary treatment for metastatic spinal tumors. However, surgical treatment may be selected to enable the patient to walk, such as in cases where paralysis of both legs occurs relatively suddenly. In contrast, surgical removal is the only treatment option for schwannomas and meningiomas. In some cases, complete removal of ependymomas is possible without damaging the spinal cord. On the other hand, because the border of astrocytomas is unclear, radical tumor removal is difficult and in many cases a biopsy is the only option. For both ependymomas and astrocytomas, radiation therapy may be performed if the tumor remains after surgery. [Arai Hajime]

Table 15-14-4
Incidence of spinal intradural tumors (%)

Table 15-14-4

Source : Internal Medicine, 10th Edition About Internal Medicine, 10th Edition Information

Japanese:

概念
　脊髄腫瘍とは，脊椎管内に発生・伸展する新生物である．脊髄および脊髄神経，くも膜，硬膜，さらに脊椎，その周囲の軟部組織などを発生母地とする．統計学的事項　脊髄・脊椎腫瘍の発生頻度は，人口10万人あたり3人程度とされている．
発生部位による分類・頻度
　脊髄腫瘍は発生部位により硬膜外腫瘍と硬膜内腫瘍に分類されるが，その比率はほぼ2：3である．硬膜外腫瘍としては転移性腫瘍が代表的であるが，硬膜内腫瘍には髄外腫瘍と髄内腫瘍がある．髄外腫瘍としては神経鞘腫と髄膜腫，髄内腫瘍としては上衣腫と星細胞腫の頻度が高い（表15-14-4）．
1）硬膜外腫瘍：
転移性腫瘍，リンパ腫などの悪性腫瘍がほとんどを占めるが，仙骨部には脊索腫が好発する．また，神経鞘腫の一部では，硬膜内と硬膜外両方に腫瘍が存在しダンベル型を呈することがある．
2）硬膜内髄外腫瘍：
神経鞘腫は全脊髄レベルにほぼ等しく発生し，30～50歳代に多く性差はあまりない．神経線維腫症2型では，しばしば脊髄に神経鞘腫が多発する．これに対して髄膜腫は，大孔付近と胸椎部に好発し，40～60歳代の女性に多い．
3）硬膜内髄内腫瘍：
星細胞腫は頸髄，頸胸髄に好発し，小児から20歳代に発生のピークがある．10歳以下の症例では，髄内腫瘍の約90％は星細胞腫とされている．小児例では良性のものが圧倒的に多いが，成人例では約25％は悪性（退形成性星細胞腫，膠芽腫）である．上衣腫は，成人の髄内腫瘍のうち発生頻度が最も高い．
臨床症状
　脊髄腫瘍の初発症状は，腫瘍の局在にかかわらず痛みであることが多い．悪性腫瘍の硬膜外転移では，背部痛や根性痛が出現した後に，数日場合によっては数時間の経過で両下肢麻痺が出現する．これに対して硬膜内腫瘍では，症状の進行は比較的緩徐で症状発現から診断までに1～2年を経ることもめずらしくない．硬膜内髄外腫瘍は通常，脊椎管内に偏在するため脊髄への圧迫は非対称性に起こり，その結果Brown-Séquard症候群をきたすことになる．すなわち，腫瘍の脊髄レベル以下に，病変と同側の運動麻痺，深部知覚低下，対側の温痛覚低下をみる．一方，硬膜内髄内腫瘍では，病変の脊髄レベル以下の運動・感覚機能が全般的に障害されるが，仙髄領域の温痛覚は保たれるといったsacral sparingをみることがある．
診断
　脊髄腫瘍の診断には原則的にMRIが用いられるが，腫瘍の存在に伴う骨変化の診断には脊椎単純X線撮影，CTが有用である．転移性腫瘍では，造影される腫瘍が硬膜外から脊髄を圧迫ないし絞扼するさまをとらえることができるが，しばしば椎体などの骨組織にも転移病巣をみる．神経鞘腫，髄膜腫はともによく造影され，脊髄は腫瘍によって偏位する．神経鞘腫は神経根の走行に沿うように伸展し，ときに硬膜外にまで及ぶが，腫瘍は脊髄の側方に位置する（図15-14-8A）．一方，髄膜腫では脊髄の腹側あるいは腹外側の硬膜に付着する腫瘍を認める．硬膜内髄内腫瘍では，脊髄は腫瘍により紡錘状に腫大する．上衣腫は腫大した脊髄のほぼ中央に強く造影される病変として描出され（図15-14-8B），その上極と下極には囊胞を高頻度に合併する．これに対して星細胞腫では，症例により腫瘍の造影効果にかなりの差があり，また病変の辺縁は上衣腫に比べ不明瞭である．
治療・予後
　悪性腫瘍の硬膜外転移に対する治療には，外科的治療，放射線治療，さらに化学療法などがある．このなかで放射線治療は有効性も高く，転移性脊髄腫瘍に対して第一義的に行われる治療法である．ただし，両下肢麻痺が比較的急激に発症した場合など，患者を歩行可能な状態にすることを目的に外科的治療が選択されることもある．これに対して，神経鞘腫や髄膜腫では外科的摘出が唯一の治療選択になる．上衣腫に関しては，症例によっては脊髄を損傷することなく腫瘍の全摘出が可能である．一方，星細胞腫では腫瘍の境界が不明瞭なため，根治的な腫瘍除去は困難で生検で終わらざるを得ない場合が多い．上衣腫，星細胞腫ともに，手術後に腫瘍が残存していれば放射線治療を行うこともある．［新井　一］

表15-14-4
脊髄硬膜内腫瘍別頻度（％）">

表15-14-4

出典　内科学第10版内科学第10版について　情報

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