Biomechanical implications of unilateral facetectomy, unilateral facetectomy plus partial contralateral facetectomy, and complete bilateral facetectomy in minimally invasive transforaminal interbody fusion.

OBJECTIVE: Minimally invasive transforaminal interbody fusion techniques vary among surgeons. One decision point is whether to perform a unilateral facetectomy (UF), a unilateral facetectomy plus partial contralateral facetectomy (UF/PF), or a complete bilateral facetectomy (CBF). The authors therefore compared the biomechanical benefits of all 3 types of facetectomies to determine which approach produces improved biomechanical outcomes. METHODS: Seven human cadaveric specimens (L3-S1) were potted and prepped for UF, with full facet removal, hemilaminectomy, discectomy, and pedicle screw placement. After distraction, a fixed interbody spacer was placed, and compression was performed. A final fixation configuration was performed by locking the rods across the screws posteriorly with bilateral compression. Final lordosis angle and change and foraminal height were measured, and standard nondestructive flexibility tests were performed to assess intervertebral range of motion (ROM) and compressive stiffness. The same procedure was followed for UF/PF and CBF in all 7 specimens. RESULTS: All 3 conditions demonstrated similar ROM and compressive stiffness. No statistically significant differences occurred with distraction, but CBF demonstrated significantly greater change than UF in mean foraminal height after bilateral posterior compression (1.90 ± 0.62 vs 1.00 ± 0.45 mm, respectively, p = 0.04). With compression, the CBF demonstrated significantly greater mean ROM than the UF (2.82° ± 0.83° vs 2.170° ± 1.10°, p = 0.007). The final lordosis angle was greatest with CBF (3.74° ± 0.70°) and lowest with UF (2.68° ± 1.28°). This finding was statistically significant across all 3 conditions (p ≤ 0.04). CONCLUSIONS: Although UF/PF and CBF may require slightly more time and effort and incur more risk than UF, the potential improvement in sagittal balance may be worthwhile for select patients.

Tailoring selection of transforaminal interbody spacers based on biomechanical characteristics and surgical goals: evaluation of an expandable spacer.

OBJECTIVE: Transforaminal lumbar interbody fusion (TLIF) is commonly used for lumbar fusion, such as for foraminal decompression, stabilization, and improving segmental lordosis. Although many options exist, surgical success is contingent on matching design strengths with surgical goals. The goal in the present study was to investigate the effects of an expandable interbody spacer and 2 traditional static spacer designs in terms of stability, compressive stiffness, foraminal height, and segmental lordosis. METHODS: Standard nondestructive flexibility tests (7.5 N⋅m) were performed on 8 cadaveric lumbar specimens (L3-S1) to assess intervertebral stability of 3 types of TLIF spacers at L4-5 with bilateral posterior screw-rod (PSR) fixation. Stability was determined as range of motion (ROM) in flexion-extension (FE), lateral bending (LB), and axial rotation (AR). Compressive stiffness was determined with axial compressive loading (300 N). Foraminal height, disc height, and segmental lordosis were evaluated using radiographic analysis after controlled PSR compression (170 N). Four conditions were tested in random order: 1) intact, 2) expandable interbody cage with PSR fixation (EC+PSR), 3) static ovoid cage with PSR fixation (SOC+PSR), and 4) static rectangular cage with PSR fixation (SRC+PSR). RESULTS: All constructs demonstrated greater stability than the intact condition (p < 0.001). No significant differences existed among constructs in ROM (FE, AR, and LB) or compressive stiffness (p ≥ 0.66). The EC+PSR demonstrated significantly greater foraminal height at L4-5 than SRC+PSR (21.1 ± 2.6 mm vs 18.6 ± 1.7 mm, p = 0.009). EC+PSR demonstrated higher anterior disc height than SOC+PSR (14.9 ± 1.9 mm vs 13.6 ± 2.2 mm, p = 0.04) and higher posterior disc height than the intact condition (9.4 ± 1.5 mm vs 7.1 ± 1.0 mm, p = 0.002), SOC+PSR (6.5 ± 1.8 mm, p < 0.001), and SRC+PSR (7.2 ± 1.2 mm, p < 0.001). There were no significant differences in segmental lordosis among SOC+PSR (10.1° ± 2.2°), EC+PSR (8.1° ± 0.5°), and SRC+PSR (11.1° ± 3.0°) (p ≥ 0.06). CONCLUSIONS: An expandable interbody spacer provided stability, stiffness, and segmental lordosis comparable to those of traditional nonexpandable spacers of different shapes, with increased foraminal height and greater disc height. These results may help inform decisions about which interbody implants will best achieve surgical goals.

A boy with arachnoid cyst, a fall, and temporary and reversible visual impairment.

BACKGROUND: Temporal arachnoid cysts have been shown to interfere with the function of nervous structures, both cerebral cortex and cranial nerves. METHODS AND RESULTS: In this case report we describe a boy with a left temporal arachnoid cyst with a sudden onset of visual impairment 4 days after a mild trauma to the head. A perimetry test revealed a complete nasal hemianopia of the left eye, which normalized rapidly after an emergency craniotomy with cyst fenestration 3 hours after the patient experienced the reduced vision. CONCLUSIONS: The observed, reversible effect on vision is most probably caused by pressure exerted by the medial part of the cyst on the left optic nerve. We believe this is the first time such a case has been described.

Primary intracranial myxoma of the parietal region. Illustrated case report.

An extremely rare case of primary intracranial myxoma mimicking an intraaxial parenchymal tumour is reported. A 25 year old male presented with complaints of headache and right sided hemiparesis. A gross total resection of the tumour was achieved. Histology confirmed that the tumour was a myxoma. Investigations did not reveal any underlying cardiac focus. Following surgery, the patient had rapid recovery from his symptoms and on a follow up at 3 months was asymptomatic. Primary intracranial myxomas are extremely rare and this is the fifth reported case in neurosurgical literature and third report of supratentorial myxoma. Though metastatic myxomas from atrial myxomas are known to occur primary intracranial myxomas are extremely rare. Surgical resection provides an excellent prognosis and the surgical aim should be to achieve total resection.

Hemangioblastoma of the filum terminale.

A 52-year-old man presented with low backache, paraesthesiae and spasticity of both lower limbs. He had urinary retention and constipation. Investigations revealed a vascular intradural cauda equina-conus tumor. MRI scan demonstrated an enhancing mass at the second and third lumbar vertebral levels. There were multiple dilated and tortuous veins draining from both poles of the tumor. Digital subtraction spinal angiogram showed the tumor to be supplied mainly by the radiculo-medullary artery from first lumbar artery and dural branches of the second and third lumbar arteries. At surgery, after pre-operative embolization, a well-defined tumor with an orange hue and fleshy consistency was encountered arising from the filum terminale. The tumor was excised en bloc. A sporadic hemangioblastoma arising from the filum terminale should be considered as a rare cause of back pain and sciatica. Total excision of the tumor offers cure.

Spontaneous cerebrospinal fluid rhinorrhea following excision of a massive torcular meningioma.

A massive supratentorial torcular meningioma was completely resected in a 50-year-old woman. On the tenth postoperative day she presented with spontaneous cerebrospinal fluid (CSF) rhinorrhea. The site of the CSF leak was through the region of the cribriform plate, remote from the site of surgery. The possible cause of the leak and the relationship with the massive meningioma are analyzed.

Cerebellar oligodendroglioma in a young adult.

A rare case of an oligodendroglioma of the cerebellum in an 18-year-old male is presented. Radical surgical excision and craniospinal radiotherapy appear to be the treatment options for these potentially malignant lesions.

Ossified ligamentum flavum of the atlantoaxial region.

A 30-year-old male presented complaining of a six-month history of progressive weakness and paraesthesia in all four limbs. Symptoms occurred following moderately severe neck trauma. Investigations revealed ossification of the ligamentum flavum (OLF) between the atlas and axis, with marked cord compression. The patient showed remarkable neurological recovery following excision of the OLF. OLF causing cord compression is rare and has never been reported in the atlantoaxial region.

Segmental costovertebral malformation associated with lipomyelomeningocoele.

We describe 2 patients with segmental costovertebral malformation, a form of spondylocostal dysostosis, associated with tethering of the conus to a lipomyelomeningocoele. Such an association is rare. In both these patients the defects occurred sporadically. The relevant literature is reviewed.