The prime objective in the surgical treatment of basilar impression (BI), Chiari malformation (CM) and/or syringomyelia (SM) is based on the restoration of the normal cerebrospinal fluid (CSF) dynamics at the craniovertebral junction through the creation of a large artificial cisterna magna. A small suboccipital craniectomy has been emphasized to avoid caudal migration of the hindbrain structures into the vertebral canal. Nevertheless, the results showed downward migration of the hindbrain related to that type of craniectomy. The authors present, otherwise, the results of 104 cases of BI, CM and/or SM, whose surgical treatment was characterized by a large craniectomy with the patient in the sitting position, tonsillectomy, large opening of the fourth ventricle and duraplasty with creation of a large artificial cisterna magna. A significant upward migration of the posterior fossa structures was detected by postoperative magnetic resonance imaging. Key words: basilar impression, Chiari malformation, hindbrain herniation, tonsillectomy, craniovertebral decompression, syringomyelia.Descompressão da fossa posterior com tonsilectomia em 104 casos de impressão basilar, malformação de Chiari e/ou siringomielia RESUMO O principal objetivo no tratamento cirúrgico da impressão basilar, malformação de Chiari e/ou siringomielia fundamenta-se na restauração dinâmica do líquido cefalorraqueano ao nível da transição craniovertebral e criação de ampla cisterna magna. Uma craniectomia suboccipital de pequenas dimensões foi proposta para evitar a migração caudal de estruturas rombencefálicas no canal vertebral. Entretanto, os resultados evidenciaram migração caudal do rombencéfalo. Os autores apresentam, por outro lado, os resultados de 104 casos de malformação de Chiari e/ou siringomielia, nos quais o tratamento cirúrgico se baseou em ampla craniectomia com o paciente em posição sentada, tonsilectomia, abertura ampla do quarto ventrículo e enxerto dural com consequente criação de ampla cisterna magna. Uma significante migração cranial das estruturas da fossa posterior foi detectada pelo emprego pós-operatório da ressonância magnética. Palavras-Chave: impressão basilar, malformação de Chiari, herniação rombencefálica, tonsilectomia, descompressão craniovertebral, siringomielia.
The authors describe ten cases of syringomyelia without hindbrain herniation depicted by preoperative magnetic resonance imaging (MRI) in supine position. However, the herniation was observed in all cases during the operation with the patient in sitting position. The postoperative MRI revealed an intense reduction of the syrinx in all patients, as well as it was also observed a clinical amelioration in all cases. The surgical treatment was based on a large craniectomy with the patient in sitting position, tonsillectomy, large opening of the fourth ventricle and duraplasty with creation of a large cisterna magna. Key words: Chiari malformation, syringomyelia, craniovertebral decompression.Resolução de siringomielia em dez casos de malformação de Chiari observada apenas com o paciente em posição sentada durante a descompressão da fossa posterior RESUMO Os autores descrevem 10 casos de siringomielia sem herniação do rombencéfalo, observada na ressonância magnética realizada em decúbito dorsal. Por outro lado, a herniação foi observada em todos os pacientes durante a operação com o paciente em posição sentada. A ressonância magnética pós-operatória evidenciou redução da cavidade siringomiélica nos dez pacientes, bem como foi observada melhora clínica em todos os casos. O tratamento cirúrgico consistiu de craniectomia ampla da fossa posterior, tonsilectomia, abertura ampla do quarto ventrículo e duroplastia com a criação de ampla cisterna magna. Palavras-chave: malformação de Chiari, siringomielia, descompressão craniovertebral.
-The Chiari malformation (CM) is characterized by variable herniation of one or both cerebellar tonsils, associated or not with displacement of the hindbrain structures into the vertebral canal. This is a retrospective study of 29 patients with CM submitted to surgical procedure between 1990 and 2003. There were 14 females and 15 males whose ages ranged from 16 to 65 years. There were seven patients with isolated CM, 12 associated with syringomyelia (SM), three associated with basilar impression (BI) and seven associated with SM and BI. The surgery was based on posterior fossa decompression. In seven patients a catheter was introduced from the subarachnoid space into the III ventricle and five were submitted to tonsillectomy. Twenty-one patients improved, one worsened, one remained unchanged, four missed follow up and two died. We conclude that the best results with CM surgery are obtained by an effective posterior fossa decompression. Those CM cases associated with other abnormalities, such as SM and BI, probably need complementary techniques which will be the theme for new prospective studies.Key WordS: Chiari malformation, posterior fossa, hindbrain malformations, surgical treatment. Estudo retrospectivo de pacientes com malformação de Chiari tratados cirurgicamenteResumo -A malformação de Chiari (MC) é o deslocamento variável de uma ou ambas as tonsilas cerebelares para o canal vertebral. este trabalho é um estudo retrospectivo de pacientes com MC tratados com cirurgia de 1990 até 2003. Foram analisados 29 prontuários, sendo 15 pacientes do sexo masculino e 14 do feminino, com idade variando entre 16 a 65 anos. destes, sete só apresentavam MC, 12 tinham MC associada com siringomielia (SM), três associada com impressão basilar (IB) e sete associada com SM e IB. Foi realizada descompressão da fossa posterior e plástica da dura-máter em todos. em sete pacientes, foi acrescida a colocação de catéter do espaço subaracnóideo para o interior do IV ventrículo e em cinco a tonsilectomia. ocorreu melhora dos sintomas em 21 pacientes, um permaneceu inalterado, houve piora em um caso, quatro não tiveram seguimento e dois faleceram. Conclui-se que a boa evolução da MC está relacionada com a descompressão efetiva da fossa posterior. os casos de MC associadas a outras malformações, como IB e SM, talvez necessitem variações técnicas, as quais serão temas de novos estudos prospectivos.
-A 29-year-old woman with acute lancinating headache, throbbed nuchal pain and subacute paraparesis underwent brain MRI in supine position that depicted: the absence of the cisterna magna, filled by non herniated cerebellar tonsils and compression of the brain stem and cisternae of the posterior fossa, which are aspects of the impacted cisterna magna without syringomyelia and without hydrocephalus. During eight days, pain was constant and resistant to drug treatment. Osteodural-neural decompression of the posterior fossa, performed with the patient in sitting position, revealed: compression of the brainstem, fourth ventricle and foramen of Magendie by herniated cerebellar tonsils, which were aspirated. Immediately after surgery, the headache and nuchal pain remmited. MRI depicted the large created cisterna magna and also that the cerebellar tonsils did not compress the fourth ventricle, the foramen of Magendie and the brainstem, besides the enlargement of posterior fossa cisternae. Four months after surgery, headache, nuchal pain and paraparesis had disappeared but hyperactive patellar and Achilles reflexes remained.KEY WORDS: headache, nuchal pain, craniovertebral malformation, tight cisterna magna, impacted cisterna magna, Chiari malformation, posterior fossa decompression, paraparesis, herniated tonsils.Cisterna magna impactada sem siringomielia associada a cefaléia lancinante, dor na nuca terebrante e paraparesia tratadas com descompressão da fossa posterior RESUMO -Uma paciente de 29 anos de idade com quadro agudo de cefaléia lancinante, dor terebrante na nuca e paraparesia subaguda foi submetida a RM do encéfalo, em posição supina, que revelou: ausên-cia da cisterna magna, preenchida por tonsilas cerebelares não herniadas e compressão do tronco encefá-lico e das cisternas da fossa posterior, compatíveis com o diagnóstico de cisterna magna impactada sem siringomielia e sem hidrocefalia. Por oito dias a dor foi constante e resistente aos analgésicos. Com a paciente em posição sentada, foi realizada descompressão osteodural-neural da fossa posterior associada a aspiração das tonsilas cerebelares. Os achados perioperatórios foram caracterizados por herniação das tonsilas cerebelares que comprimiam o tronco cerebral, o quarto ventrículo e o forame de Magendie. No pós-operatório imediato houve remissão da cefaléia e da dor na nuca. A RM evidenciou a cisterna magna recém-criada, alargamento do quarto ventrículo e das cisternas do tronco encefálico. Quatro meses depois, a paciente continuava sem cefaléia, sem dor na nuca e sem paraparesia. Entretanto, permaneceu a hiperatividade dos reflexos patelares e aquileus.
-We re p o rt on a 48 years-old man with basilar impression without syringohydromyelia, in which the cisterna magna was impacted by the cerebellar tonsils. Six months after posterior fossa decompre s s i o n there was the disappearance of nuchal rigidity, vertigo, spastic paraparesis and improvement of balance. Nevertheless hyperreflexia and diminished pallesthesia of the lower limbs persisted.KEY WORDS: basilar impression, Chiari malformation, syringomyelia, posterior fossa decompression, tight cisterna magna.I m p ressão basilar associada com cisterna magna impactada, paraparesia espástica e distúrbios do equilíbrio: relato de caso RESUMO -O presente relato descreve um homem de 48 anos com impressão basilar, sem siringo-hidro m i e l i a , no qual a cisterna magna se achava impactada pelas tonsilas cere b e l a res. O quadro clínico era caracterizado, especialmente, por paraparesia espástica. Seis meses após a descompressão da fossa posterior houve re g ressão da rigidez de nuca, vertigem, paraparesia espástica inicialmente observadas e melhora do equilíbrio. A hiperreflexia e a hipopalestesia persistiram nos membros inferiores.PA L AV R A S -C H AVE: impressão basilar, malformação de Chiari, siringomielia, descompressão da fossa posterior, cisterna magna impactada.Hans Chiari 1 , 2 (1891, 1895) described four types of c e rebellar anomalies. Type I was characterized by d o w n w a rd displacement of the cerebellar tonsils and the medial portions of the inferior cerebellar lobes, which accompanied the medulla into the cervical spinal canal. The type II showed downward displacement of portions of the cerebellum (1891), and portions of the inferior vermis (1895), pons, medulla oblonga and, at least, a part of lengthened fourt h ventricle, which reached the disc C 4 -C 5, into the enlarged cervical spinal canal. In type III, the hydrocephalic cerebellum, pons and medulla were inside a cervical meningocele (hydroencephaloceles cerebellaris cervicalis), through a spina bifida of the first three cervical vertebrae. In type IV, there was hypoplasia of the cerebellum without herniation of cerebellar stru c t u res into the spinal canal. Iskandar et al. 3(1998) related five cases of siringohydromyelia (SM), in which the cisterna magna was filled by the cerebellar tonsils. In all five cases there was clinical improvement after decompression of the posterior fossa and a marked reduction in the size of syrinx. These authours admitted that this dramatic response to d e c o m p ression indicates that this entity has a Chiarilike pathophysiology. On the other hand, Kyoshima et al. 4 related four similar cases with impro v e m e n t in symptoms and a reduction in syrinx size in thre e patients, and a reduction in ventricle size in two. These authors named the impacted cisterna magna by the cerebellar tonsils "tight cisterna magna", and called the description according to Iskandar et al.3 , "Chiari "0" malformation".
-We re p o rton a 49 year old man with impacted cisterna magna without the presence of syringoh y d romyelie (SM). The clinical picture was characterized by spastic paraparesis. Magnetic resonance imaging depicted a cisterna magna filled by the cerebellar tonsils. Six months after osteodural-neural decomp ression of the posterior fossa there was resolution of neurological symptoms and signs with the exception of hyperactive patellar and Achilles reflexes.KEY WORDS: tight cisterna magna, impacted cisterna magna, Chiari malformation, posterior fossa decompression, spastic paraparesis. Relatamos o caso de paciente de 49 anos com cisterna magna impactada sem a pre s e n ç a de siringo-hidromielia (SM). O quadro clínico caracterizava-se por paraparesia espástica. A re s s o n â n c i a magnética evidenciou a cisterna magna preenchida pelas tonsilas cerebelares. Seis meses após a descomp ressão osteodural-neural da fossa posterior, houve resolução dos sintomas e sinais neurológicos, com exceção da hiperatividade dos reflexos patelares e aquileus.PA L AV R A S -C H AVE: cisterna magna impactada, malformação de Chiari, descompressão da fossa posterior, paraparesia espástica.Hans Chiari 1 , 2 described four types of cere b e l l a r anomalies (CM). Type I characterized by downward displacement of the cerebellar tonsils and the medial portions of the inferior cerebellar lobes which accompanied the medulla into the cervical spinal canal. Type II showed downward displacement of port i o n s of the cerebellum (1891), and portions of the inferior vermis (1895), pons, medulla oblonga and, at least, p a rt of lengthened fourth ventricle, which re a c h e d the disc C 4-C 5, into the enlarged cervical spinal canal. In type III, the hydrocephalic cerebellum, pons and medulla oblonga were inside a cervical meningocele (hydroencephaloceles cerebellaris cerv i c a l i s ) , t h rough a spina bifida of the first three cervical vertebrae. In type IV, there was hipoplasia of the cerebellum without herniation of cerebellar stru c t u res into the spinal canal. Iskandar et al. 3 (1998) related five cases of syringohidromyelia (SM), in which the cist e rna magna was filled by the cerebellar tonsils. After d e c o m p ression of the posterior fossa, there was clinical improvement, as well as marked reduction in the size of the syrinx in all cases. The authors admitted t h a t this dramatic response to decompression indicates that this entity has a Chiari-like pathophysiology.
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