Threshold selection criteria for quantification of lumbosacral cerebrospinal fluid and root volumes from MRI.

BACKGROUND AND PURPOSE: The high variability of CSF volumes partly explains the inconsistency of anesthetic effects, but may also be due to image analysis itself. In this study, criteria for threshold selection are anatomically defined. METHODS: T2 MR images (n = 7 cases) were analyzed using 3-dimentional software. Maximal-minimal thresholds were selected in standardized blocks of 50 slices of the dural sac ending caudally at the L5-S1 intervertebral space (caudal blocks) and middle L3 (rostral blocks). Maximal CSF thresholds: threshold value was increased until at least one voxel in a CSF area appeared unlabeled and decreased until that voxel was labeled again: this final threshold was selected. Minimal root thresholds: thresholds values that selected cauda equina root area but not adjacent gray voxels in the CSF-root interface were chosen. RESULTS: Significant differences were found between caudal and rostral thresholds. No significant differences were found between expert and nonexpert observers. Average max/min thresholds were around 1.30 but max/min CSF volumes were around 1.15. Great interindividual CSF volume variability was detected (max/min volumes 1.6-2.7). CONCLUSIONS: The estimation of a close range of CSF volumes which probably contains the real CSF volume value can be standardized and calculated prior to certain intrathecal procedures.

Cefalea pospunción dural. Ultraestructura de las lesiones durales y agujas espinales usadas en las punciones lumbares / Post dural puncture cephalea. UItra-structure of the dural lesions and spinal needles used in lumbar punctures

Con el microscopio electrónico de barrido, se examinó la morfología de las lesiones durales y aracnoideas en muestras de saco dura-aracnoideo extraídos de cuerpos humanos recién fallecidos. Después de hacer punciones con agujas Quincke y Whitacre 22-G y 25-G, no se encontraron diferencias estadísticamente significativas entre las áreas de las lesiones durales y aracnoideas. La lesión tenía una morfología diferente con cada aguja. La aguja Whitacre producía una lesión de bordes rotos con gran destrucción de fibras durales, mientras que la aguja "biselada" Quincke causaba una lesión con forma de "U" o "V", como la tapa de una lata, con bordes de corte limpio. La alineación paralela o perpendicular entre el bisel de la punta de la aguja Quincke y el eje del axis no modificaba el área de las lesiones durales y aracnoideas. Se analizó cómo se puede producir cada tipo de lesión y se interpretaron los otros factores que podrían participar. Con la misma técnica se estudiaron agujas espinales nuevas obteniéndose, en cierto porcentaje de éstas, una imagen tridimensional a gran aumento de la fragmentación de puntas, defectos del pulido y existencia de rebabas. Se analizó cómo se pueden alterar las puntas de las agujas al chocar contra el hueso y de qué manera los defectos de estas constituyen otro aspecto de la compleja suma de variables que predisponen a la aparición de una cefalea pospunción dural.

The morphology of dural and arachnoid lesions was electronically scanned, from samples of dura-arachnoid sacs taken from recently deceased human beings. After punctures with Quincke y Whitacre 22-G y 25-G needles, no statistically significant differences were found between the areas of the dural and arachnoid lesions. The lesion had a different morphology with each needle. The Whitacre needle produced a lesion of broken edges with great destruction of the dural fibers, whereas the Quincke "beveled" needle caused a "U" or "V" shaped lesion, like the lid of a can, with clean-cut edges. The parallel or perpendicular alignment between the bevel of the Quincke needle tip and the axis of the axis did not modify the area of the dural and arachnoid lesions. A study was made of how each type of lesion could have come about and of other possible participating factors. The same technique was used to study new spinal needles and, in a certain percentage, a three dimensional image was obtained, showing a great increase in the fragmentation of the tips, burnish defects and the existence of burrs. We also analyzed how hitting against the bone could affect the tips of the needles and how their defects could be another factor in the complex sum of variables that predispose the patient to suffer post dural puncture cephalea.

Com o microscópio eletrônico de varredura, examinou-se a morfologia das lesoes durais e da aracnóide em amostras de saco dural-aracnóideo extraídos de corpos humanos de recem-falecidos. As diferencas entre as áreas das lesoes durais e da aracnóide pós-puncao com agulhas Quincke e Whitacre 22-G e 25-G nao foram estatisticamente significativas, e a morfologia da lesao causada com cada agulha foi diferente. A agulha Whitacre provocou lesao de bordas rompidas com grande destruicao de fibras durais, enquanto a agulha "biselada" Quincke causou lesao com forma de "U" ou "V", como a tampa de uma lata, com bordas de corte limpo. O alinhamento paralelo ou perpendicular do bisel da ponta da agulha Quincke com o eixo do áxis nao modificou a área das lesóes durais e da aracnóide. Foram analisadas as causas de cada tipo de lesao e interpretados outros fatores envolvidos. Utilizando a mesma técnica, avaliaram-se imagens tridimensionais de algumas agulhas espinhais novas tiradas com grande aumento: fragmentacao das pontas, defeitos de polimento e presenca de rebarbas. Avaliou-se também como se modificam as pontas das agulhas ao atingirem o osso e a influência dos defeitos das pontas na complexa soma de variáveis que predispoem o aparecimento de cefaléia pós-puncao dural.

Evaluation of intervertebral disc herniation and hypermobile intersegmental instability in symptomatic adult patients undergoing recumbent and upright MRI of the cervical or lumbosacral spines.

PURPOSE: The purpose of the study was to determine the difference in findings between recumbent and upright-sitting MRI of the cervical and lumbosacral spine in patients with related sign and symptoms. MATERIALS AND METHODS: A total of 89 patients were studied (lumbosacral spine: 45 patients; cervical: 44 patients). T1-weighted (TR: 350, TE: 20) fast spin echo and T2-weighted (TR: 2500, TE: 160) fast spin echo images were acquired in the sagittal and axial planes in both the recumbent and sitting-neutral positions. The images were acquired on the Upright MRI unit (Fonar Corporation, Melville, NY). Differences were sought between the recumbent and upright-sitting positions at all levels imaged, in both planes. RESULTS: The total number of cases of pathology was 68, including instances of posterior disc herniation and anterior and posterior spondylolisthesis. Focal posterior disc herniations were noted in 55 patients (cervical: 31, lumbosacral: 24) [62% of patients]. Six of these herniations (cervical: 4, lumbosacral: 2) [11%] were seen only on the upright-sitting study. Focal posterior disc herniations were seen to comparatively enlarge in size in 35 patients on the upright-seated examination (cervical: 21, lumbosacral: 14) [72%], and reduce in size in 9 patients (cervical: 5, lumbosacral: 4) [18%]. Degenerative anterior (n: 11) and posterior (n: 2) spondylolisthesis was seen in 13 patients (cervical: 0, lumbosacral: 13) [15% of patient total]. Anterior spondylolisthesis was only seen on the upright-seated examination in 4 patients (cervical: 0, lumbosacral: 4) [31%]. Anterior spondylolisthesis was comparatively greater in degree on the upright-seated study in 7 patients (cervical: 0, lumbosacral: 7) [54%]. Posterior spondylolisthesis was comparatively greater in degree on the recumbent examination in 2 patients (cervical: 0, lumbosacral: 2) [15%]. The overall combined recumbent miss rate in cases of pathology was 15% (10/68). The overall combined recumbent underestimation rate in cases of pathology was 62% (42/68). The overall combined upright-seated underestimation in cases of pathology was 16% (11/69). CONCLUSIONS: Overall, upright-seated MRI was found to be superior to recumbent MRI of the spine in 52 patents (recumbent missed pathology [n: 10]+recumbent underestimated pathology [n: 42]=52/89 total patients: 58%) in cases of posterior disc herniation and anterior spondylolisthesis. This seems to validate the importance of weight-bearing imaging in the spine that might be expected to unmask positional enlarging disc herniations and worsening spondylolisthesis. Overall, recumbent MRI was found to be superior to upright-seated MRI in 11 cases (11/89: 12%). The latter finding was possibly due to the fact that upright seated position is actually partial flexion that might be expected to reduce some cases of hypermobile posterior spondylolisthesis.