Sectioning of the Filum Terminale in Patients with Chiari Malformation Type 1 Associated with Occult Tethered Cord Syndrome: Literature Review / Secção do filum terminale em pacientes com malformação de chiari tipo 1 associado a síndrome oculta da medula presa: revisão de literatura

Approximately 125 years ago, a group of pathologies now known as Chiari malformations was described for the first time. However, some mechanisms of its formation still remain unknown. A bibliographic survey was performed through a search in PubMed. In 1938, it was already theorized that an increase in spinal cord tension could be the cause of Chiari malformation type 1 (CM1) tonsillar herniation. In 1953, a condition known for the anchoring of the filum terminale to the vertebral canal was described for the first time and would later be known as tethered cord syndrome (TCS). Some studies have shown that it is associated with increased tension in the spinal cord, and this formed the basis for a possible pathophysiological explanation of tonsillar herniation. Case series emerged reporting that treatment for TCS with the sectioning of the filum terminale (SFT) could provide clinical improvement of patients with CM1. A new pathological entity emerged when it was realized that patients with the clinical picture of TCS could have the medullary cone in its normal position, differing from the caudal migration expected for the TCS. This condition became known as occult tethered cord syndrome (OTCS). Case series attempted to demonstrate its association with the origin of CM1, a non-intuitive association, since the cone in the normal position contradicts traction as a source of tonsillar herniation. To this day, the absence of randomized control trials limits any conclusions regarding the effectiveness of SFT for the treatment of patients with CM1.

Há cerca de 125 anos, era descrita pela primeira vez um grupo de patologias hoje conhecidas como malformações de Chiari. No entanto, alguns mecanismos de sua formação ainda permanecem desconhecidos. Um levantamento bibliográfico foi feito através do PubMed. Em 1938, já se teorizava que um aumento da tensão medular poderia ser a causa da herniação tonsilar da malformação de Chiari tipo 1 (MC1). Em 1953, foi descrita pela primeira vez uma condição conhecida pelo ancoramento do filum terminale ao canal vertebral e que mais tarde viria a ser conhecida como síndrome da medula presa (SMP). Alguns estudos demonstraram que ela estava associada à tensão aumentada na medula espinhal, e a partir disso estava formada a base para uma possível explicação fisiopatológica da herniação tonsilar. Séries de casos surgiram relatando que o tratamento para a SMP com a secção do filum terminale poderia proporcionar melhora clínica aos pacientes com MC1. Uma nova entidade patológica surgiu quando se percebeu que pacientes com o quadro clínico de SMP poderiam ter o cone medular em sua posição normal, diferente da migração caudal esperada para a SMP. Essa condição ficou conhecida como SMP oculta. Séries de casos tentaram demonstrar sua associação com a origem da MC1, uma associação nada intuitiva, visto que o cone na posição normal contradiz a tração como fonte da herniação tonsilar. A ausência de ensaios randomizados controlados até o dia de hoje não permite concluir a eficácia do método de secção do filum no tratamento de pacientes com MC1.

Basilar invagination associated with chiari malformation type I: A literature review.

Basilar invagination (BI) and Chiari malformation type I (CM-I) are very important anomalies that introduce instability and compression in the occipitocervical transition region and have complex clinical characteristics. These anomalies vary according to the affected structures. The present study revises current knowledge regarding the anatomy, anatomo-physiology, clinical manifestations, and radiological findings of these entities and the associated surgical treatment approaches. A bibliographic survey was performed through a search in the Medline, PubMed, SciELO, Science and LILACS databases. When associated, these craniovertebral malformations result in neurological deficits due to neural parenchyma compression; however, the presence of microtraumas due to repetitive lesions caused by the bulb and cervical marrow instability has been highlighted as a determinant dysfunction. Surgical treatment is controversial and has many technical variations. Surgery is also challenging due to the complex anatomical characteristics and biomechanics of this region. Nevertheless, advances have been achieved in our understanding of related mechanisms, and compression and atlantoaxial instability are considered key elements when selecting the surgical approach.

Basilar invagination associated with chiari malformation type I: A literature review

Basilar invagination (BI) and Chiari malformation type I (CM-I) are very important anomalies that introduce instability and compression in the occipitocervical transition region and have complex clinical characteristics. These anomalies vary according to the affected structures. The present study revises current knowledge regarding the anatomy, anatomo-physiology, clinical manifestations, and radiological findings of these entities and the associated surgical treatment approaches. A bibliographic survey was performed through a search in the Medline, PubMed, SciELO, Science and LILACS databases. When associated, these craniovertebral malformations result in neurological deficits due to neural parenchyma compression; however, the presence of microtraumas due to repetitive lesions caused by the bulb and cervical marrow instability has been highlighted as a determinant dysfunction. Surgical treatment is controversial and has many technical variations. Surgery is also challenging due to the complex anatomical characteristics and biomechanics of this region. Nevertheless, advances have been achieved in our understanding of related mechanisms, and compression and atlantoaxial instability are considered key elements when selecting the surgical approach.