Portable MRI to assess optic chiasm decompression after endoscopic endonasal resection of sellar and suprasellar lesions.

OBJECTIVE: Low-field portable MRI (pMRI) is a recent technological advancement with potential for broad applications. Compared with conventional MRI, pMRI is less resource-intensive with regard to operational costs and scan time. The application of pMRI in neurosurgical oncology has not been previously described. The goal of this study was to demonstrate the efficacy of pMRI in assessing optic nerve decompression after endoscopic endonasal surgery for sellar and suprasellar pathologies. METHODS: Patients who underwent endoscopic endonasal surgery for sellar and suprasellar lesions at a single institution and for whom pMRI and routine MRI were performed postoperatively were retrospectively reviewed to compare the two imaging systems. To assess the relative resolution of pMRI compared with MRI, the distance from the optic chiasm to the top of the third ventricle was measured, and the measurements were compared between paired equivalent slices on T2-weighted coronal images. The inter- and intrarater correlations were analyzed. RESULTS: Twelve patients were included in this study (10 with pituitary adenomas and 2 with craniopharyngiomas) with varying degrees of optic chiasm compression on preoperative imaging. Measurements were averaged across raters before calculating agreement between pMRI and MRI, which demonstrated significant interrater reliability (intraclass correlation coefficient [ICC] = 0.78, p < 0.01). Agreement between raters within the pMRI measurements was also significantly reliable (ICC = 0.93, p < 0.01). Finally, a linear mixed-effects model was specified to demonstrate that MRI measurement could be predicted using the pMRI measurement with the patient and rater set as random effects (pMRI ß coefficient = 0.80, p < 0.01). CONCLUSIONS: The results of this study suggest that resolution of pMRI is comparable to that of conventional MRI in assessing the optic chiasm position in relation to the third ventricle. Portable MRI sufficiently demonstrates decompression of the optic chiasm after endoscopic endonasal surgery. It can be an alternative strategy in cases in which cost, scan-time considerations, or lack of intraoperative MRI availability may preclude the ability to assess adequate optic nerve decompression after endoscopic endonasal surgery for sellar and suprasellar lesions.

Use of droxidopa for blood pressure augmentation after acute spinal cord injury: case reports.

Hypotension secondary to autonomic dysfunction is a common complication of acute spinal cord injury (SCI) that may worsen neurologic outcomes. Midodrine, an enteral α-1 agonist, is often used to facilitate weaning intravenous (IV) vasopressors, but its use can be limited by reflex bradycardia. Alternative enteral agents to facilitate this wean in the acute post-SCI setting have not been described. We aim to describe novel application of droxidopa, an enteral precursor of norepinephrine that is approved to treat neurogenic orthostatic hypotension, in the acute post-SCI setting. Droxidopa may be an alternative enteral therapy for those intolerant of midodrine due to reflex bradycardia. We describe two patients suffering traumatic cervical SCI who were successfully weaned off IV vasopressors with droxidopa after failing with midodrine. The first patient was a 64-year-old male who underwent C3-6 laminectomies and fusion after a ten-foot fall resulting in quadriparesis. Post-operatively, the addition of midodrine in an attempt to wean off IV vasopressors resulted in significant reflexive bradycardia. Treatment with droxidopa facilitated rapidly weaning IV vasopressors and transfer to a lower level of care within 72 hours of treatment initiation. The second patient was a 73-year-old male who underwent C3-5 laminectomies and fusion for a traumatic hyperflexion injury causing paraplegia. The addition of midodrine resulted in severe bradycardia, prompting consideration of pacemaker placement. However, with the addition of droxidopa, this was avoided, and the patient was weaned off IV vasopressors on dual oral therapy with midodrine and droxidopa. Droxidopa may be a viable enteral therapy to treat hypotension in patients after acute SCI who are otherwise not tolerating midodrine in order to wean off IV vasopressors. This strategy may avoid pacemaker placement and facilitate shorter stays in the intensive care unit, particularly for patients who are stable but require continued intensive care unit admission for IV vasopressors, which can be cost ineffective and human resource depleting.

Brainstem Dose Constraints in Nonisometric Radiosurgical Treatment Planning of Trigeminal Neuralgia: A Single-Institution Experience.

BACKGROUND: CyberKnife stereotactic radiosurgery (SRS) for trigeminal neuralgia (TGN) administers nonisometric, conformational high-dose radiation to the trigeminal nerve with risk of subsequent hypoesthesia. METHODS: We performed a retrospective, single-institution review of 66 patients with TGN treated with CyberKnife SRS to compare outcomes from 2 distinct treatment periods: standard dosing (n = 38) and reduced dosing (n = 28). Standard and reduced dosing permitted a maximum brainstem dose of 45 Gy and 25 Gy, respectively, each with a prescription dose of 60 Gy. Primary and secondary outcomes were Barrow Neurologic Institute pain and numbness scores. Maximum brainstem dose, prepontine nerve length, and treatment history were recorded for their predictive contributions by logistic regression. RESULTS: After matching, patients in the standard dosing and reduced dosing groups were followed for a median of 25 months and 19.5 months, respectively. Mean trigeminal nerve length was 8.55 mm in the standard dosing group and 9.46 mm in the reduced dosing group. Baseline rates of poorly controlled pain were 97% and 88%, respectively, which improved to 23.4% and 8.3%, respectively (P < 0.001 for both). The baseline rates of bothersome numbness were null in both groups, and increased to 25% in the standard group (P = 0.006) and to 21% in the reduced group (P = 0.07). Regression analyses suggested that reduced brainstem exposure (P = 0.01), as well as a longer trigeminal nerve (P = 0.01), were predictive of durable pain control. CONCLUSIONS: These outcomes demonstrate that a lower maximum brainstem dose can provide excellent pain control without affecting facial numbness. Longer nerves may achieve better long-term outcomes and help optimize individual plans.