When is an acoustic neuroma not an acoustic neuroma? Pitfalls for radiosurgeons.

INTRODUCTION: Because acoustic neuroma (AN), also termed vestibular schwannoma, constitutes by far the commonest intracranial schwannoma and cerebello-pontine angle (CPA) tumour, there is a risk of overlooking rarer alternative diagnoses with similar clinical and/or radiological features. The purpose of this article is to highlight to radiosurgeons the potentially serious implications of this problem through illustrative case studies. METHODS: Our linac stereotactic radiosurgery (SRS) technique has been previously described, with stereotactic headring fixation and treatment delivered via cones or micro-multileaf collimators using multiple arcs or static beams. RESULTS: Between November 1993 and October 2014, we treated 132 patients referred with a clinical diagnosis of AN, the vast majority with 12 Gy marginal dose. Three of these (2.3%), evident either at the time of treatment (2) or subsequently (1), had features instead consistent with cochlear schwannoma, facial schwannoma and meningioma, respectively. Each warranted significant modification to standard AN outlining and fields. The meningioma progressed due to geographic miss. One other patient with recurrent facial schwannoma (not yet needing SRS) was also referred with an incorrect diagnosis of AN. CONCLUSION: When rare variants of common medical problems are not identified before referral, there is a risk that 'blinkering' can lead to misdiagnosis and suboptimal treatment. Radiosurgeons need to be particularly mindful of this issue with AN, which can mimic several other tumours occurring in the CPA region, albeit with different patterns of spread. Optimal imaging, high-quality radiology reporting and neuroradiology input at the time of SRS planning within the setting of a specialised multidisciplinary team are highly desirable.

LINAC radiosurgery for cerebral arteriovenous malformations: a single centre prospective analysis and review of the literature.

Stereotactic radiosurgery (SRS) is a well established, minimally invasive treatment option for patients diagnosed with cerebral arteriovenous malformations (AVM). We present the experience in linear accelerator-based SRS for cerebral AVM treated over 14 years. We prospectively followed 67 patients with 69 AVM treated with SRS from 1994 to 2008, inclusive. The mean patient age was 37 years (range 7-69) with 36 women and 31 men. The median AVM size, as defined by maximal diameter, was 2.5 cm (range 0.5-4.6 cm) and the median marginal dose was 18 Gy in one fraction. The crude angiographic obliteration rate was 55% with a 3 and 5 year actuarial rate of 39% and 65%, respectively. Median time to obliteration was 4.2 years. Higher treatment dose (p<0.0001) and smaller maximal AVM diameter (p=0.002) were associated with an increased obliteration rate. There were no deaths from treatment. Post-treatment neurological complications occurred in 10 patients (15%) including hemorrhage in two. Twelve patients (18%) required a second SRS procedure. Larger AVM diameter was associated with increased odds of requiring re-treatment (p=0.02). Radiosurgery for intracerebral AVM is a non-invasive therapeutic option with low morbidity and a reasonable likelihood of nidus obliteration. Treatment dose and AVM diameter are the main determinants of obliteration.

Enhanced intrinsic radiosensitivity after treatment with stereotactic radiosurgery for an acoustic neuroma.

Enhanced radiosensitivity is an uncommon phenomenon attributable to deficient DNA repair after radiotherapy which can be assessed with the γ-H2AX assay. Reports of radiosensitivity after stereotactic radiosurgery (SRS) are uncommon. We describe a case where the clinical, radiological and laboratory findings suggest enhanced radiosensitivity after SRS for an acoustic neuroma.

Hearing preservation after low dose linac radiosurgery for acoustic neuroma depends on initial hearing and time.

PURPOSE: To assess long term outcomes and factors determining hearing preservation after low dose linac stereotactic radiosurgery (SRS) for acoustic neuroma (AN) at the Royal Adelaide Hospital using prospectively collected data. MATERIAL AND METHODS: Between 1994 and 2010, 102 patients had SRS for AN. Five patients had neurofibromatosis type 2, six sporadic cases had relapsed after surgery, and the remaining 91 sporadic cases had primary SRS. Dose was 12 or 14 Gy. Sustained changes ≥ 2 mm in any diameter were deemed significant, and useful hearing was defined as inter-aural pure tone average (PTA) ≤ 50 dB. Possible prognostic factors for hearing retention were tested by dividing the patients at pre-specified cutpoints: age (60 years), maximum tumour diameter (20mm), initial PTA (20 dB) and dose (12 vs 14 Gy). RESULTS: Eighty-four of the 91 sporadic primary SRS cases were evaluable for tumour control with at least one post-treatment MRI. Their median follow-up was 65 mo (range 10-184 mo). Eighty-two (97.6%) were controlled, the remaining two requiring salvage surgery for progression at 5.75 and 9.75 years. Also, one of the post-operative cases required surgery at 2.1 years after SRS. For the 50 sporadic primary SRS patients with initially useful hearing, median age was 56 (range 21-76), median initial PTA 16 dB (range -11 to +45 dB) and median tumour diameter 21 mm (range 10-33 mm). Four received 14 Gy, the rest 12 Gy. After SRS, 19 patients (38%) retained useful hearing. The Kaplan-Meier estimated preservation rate at 5 years was 50% (95% CI 36-64%) but by 10 years, this had fallen to 23% (95% CI 12-41%). On univariate analysis, the only significant factor was initial PTA (P < 0.0001). The estimated risk of hearing loss after SRS for patients with initial PTA ≥ 20 dB was 5.0 (95% CI 2.2-11.2) times that with PTA < 20 dB. CONCLUSIONS: Tumour control was excellent (99/102=97% freedom from surgical salvage). Hearing preservation was strongly dependent on initial PTA, but there was a steady fall-off in hearing out to at least 10 years.

Preoperative magnetic resonance imaging in Type 2 trigeminal neuralgia.

OBJECT: Trigeminal neuralgia (TN) is a neuropathic pain syndrome that is often associated with neurovascular compression of the trigeminal nerve and may be effectively treated with microvascular decompression (MVD). The authors used high-resolution MR imaging with 3D reconstruction in patients with constant facial pain (Type 2 TN) to determine the presence/absence of neurovascular compression and thus a potential MVD benefit. They retrospectively contacted patients to evaluate outcome. METHODS: All patients who reported spontaneous onset of constant facial pain (Type 2 TN), which occurred at least 50% of the time, who had undergone high-resolution 3-T MR imaging with 3D reconstruction were retrospectively selected for this study. Clinical history, facial pain questionnaire data, physical examination findings, and results from 3-T 3D MR imaging reconstruction were recorded for all patients. Intraoperative findings and clinical pain outcome were recorded for all patients who underwent MVD. RESULTS: Data obtained in 27 patients were assessed. On the basis of history and 3D MR imaging reconstruction findings, 13 patients were selected for MVD (Group A) and 14 underwent conservative treatment (Group B). Typical or suspected artery- or vein-induced neurovascular compression was predicted preoperatively in 100% of Group A patients and in 0% of Group B patients. At the time of MVD, definitive neurovascular compression was confirmed in 11 (84.6%) of 13 Group A patients. Following MVD, facial pain was completely relieved in 3 (23%), improved in 7 (53.8%), and no better in 3 (23%) of 13 Group A patients. A history of episodic (Type 1 TN) pain at any time was reported in 100 and 50% of Group A and Group B patients, respectively. A Type 1 TN pain component was reportedly improved/relieved in all Group A patients, but the Type 2 TN pain component was improved in only 7 (53.8%) of 13 patients. The mean postoperative follow-up duration was 13 months. CONCLUSIONS: High-resolution 3D MR imaging reconstruction in patients with constant facial pain (Type 2 TN) can help determine the presence/absence of neurovascular compression. Surgical selection based on both clinical and radiological criteria has the potential to improve surgical outcome in patients with Type 2 TN who may potentially benefit from MVD. However, even in such selected patients, pain relief is likely to be incomplete.

Long-term outcome following ilioinguinal neurectomy for chronic pain.

OBJECT: Ilioinguinal neuralgia is one cause of chronic groin pain following inguinal hernia repair, and it affects approximately 10% of patients. Selective ilioinguinal neurectomy is one proposed treatment option for carefully selected patients. The goal of this study was to determine the long-term outcome of patients who underwent selective ilioinguinal neurectomy for chronic post-hernia pain. METHODS: The authors retrospectively reviewed the clinical assessment, surgical treatment, and long-term outcome in 26 patients with ilioinguinal neuralgia who underwent selective ilioinguinal neurectomy performed by the senior author (K.J.B.) at Oregon Health & Science University between 1998 and 2008. Data were collected from patient charts and a follow-up telephone questionnaire. RESULTS: Twenty-six patients (14 men and 12 women) had a clinical diagnosis of ilioinguinal neuralgia based on a history of radiating neuropathic groin, medial thigh, and genitalia pain. One patient had bilateral disease (therefore there were 27 surgical cases). A selective nerve block was performed in 21 (81%) of 26 patients and was positive in 20 (77%) of the 26. In all but 2 patients, pain onset followed abdominal surgery (for hernia repair in 18 patients), and was immediate in 16 (67%) of 24 patients. The mean patient age was 48.7 years, and the mean duration of pain prior to neurosurgical consultation was 3.9 years. Surgery was performed after induction of local or general anesthesia in 17 and 10 cases, respectively. The ilioinguinal nerve was identified in 25 cases, and the genitofemoral nerve in 2, either entrapped in mesh, scar, or with obvious neuroma (22 of 27 cases). The identified nerve was doubly ligated, cut, and buried in muscle at its most proximal point. At the 2-week follow-up evaluations, 14 (74%) of 19 patients noted definite pain improvement. Nineteen (73%) of the 26 patients were contacted by telephone and agreed to participate in completing long-term follow-up questionnaires. The mean follow-up duration was 34.78 months. Return of pain was reported by 13 (68%) of 19 patients. Using a verbal numerical rating scale (0-10), pain was completely relieved in 27.8%, better in 38.9%, no better in 16.7%, and worse in 16.7% of patients. CONCLUSIONS: Ilioinguinal neurectomy is an effective and appropriate treatment for selected patients with iatrogenic ilioinguinal neuralgia following abdominal surgery. Although a high proportion of patients reported some long-term recurrence of pain, complete or partial pain relief was achieved in 66.7% of the patients observed.

Substance P immunoreactivity increases following human traumatic brain injury.

Recent experimental evidence suggests that neuropeptides, and in particular substance P (SP), are released following traumatic brain injury (TBI) and may play a significant role in the aetiology of cerebral edema and increased intracranial pressure. Whether SP may play a similar role in clinical TBI remains unknown and was investigated in the current study. Archival post-mortem material was selected from patients who had sustained TBI, had died and had undergone post-mortem and detailed neuropathological examination (n = 13). A second cohort of patients who had died, but who showed no neuropathological abnormality (n = 10), served as case controls. Changes in SP immunoreactivity were examined in the cerebral cortex directly beneath the subdural haematoma in 7 TBI cases and in proximity to contusions in the other 6 cases. Increased SP perivascular immunoreactivity was observed after TBI in 10/13 cases, cortical neurones in 12/13 and astrocytes in 10/13 cases. Perivascular axonal injury was observed by amyloid precursor protein (APP) immunoreactivity in 6/13 TBI cases. Co-localization of SP and APP in a small subset of perivascular fibres suggests perivascular axonal injury could be a mechanism of release of this neuropeptide. The abundance of SP fibres around the human cerebral microvasculature, particularly post capillary venules, together with the changes observed following TBI in perivascular axons, cortical neurones and astrocytes suggest a potentially important role for substance P in neurogenic inflammation following human TBI.

Surgical management of spinal catheter granulomas: operative nuances and review of the surgical literature.

OBJECTIVE: Spinal catheter granulomas are a rare and, most likely, underreported complication of intrathecal opioid therapy. Such granulomas can be associated with devastating neurological sequelae if not treated in a timely fashion. Most neurosurgeons, however, are unlikely to have had experience in the surgical management of this condition. CLINICAL PRESENTATION: The authors present 3 surgical cases of patients with spinal catheter granulomas with neurological deficits. One patient's intraoperative video illustrates the challenges of diagnosis, radiological assessment, and surgery for spinal catheter granulomas. INTERVENTION: All 3 patients had implanted opioid pumps for management of chronic spinal pain secondary to fracture, tethered cord, and back pain. Increasing back pain and a progressive myelopathy was observed in all patients. A clear radiological diagnosis was made more difficult because of instrumentation artifact in 1 case and claustrophobia in another. Computed tomographic myelography was necessary in 1 case. The surgical findings were: 1 extradural catheter with granuloma and 2 intradural catheters encased with granuloma and adherent to the cord. The extradural catheter was trimmed of granuloma and replaced intradurally in 1 case. The patients with intradural catheter granulomas required judicious dissection of the granulomas from the dorsum of the cord, duroplasty, and catheter section. Critical intraoperative stages were recorded and are presented in digital movie format. Two patients had neurological improvement after surgery; however, 1 patient remained paraplegic. The 2 patients with catheter section required opioid withdrawal treatment. CONCLUSION: The operative management of spinal intrathecal granulomas associated with opioid infusion pumps can be challenging and depends on a high degree of clinical suspicion, imaging results, and operative findings.

Surgical management of cerebral metastases from melanoma: outcome in 147 patients treated at a single institution over two decades.

OBJECT: The aim of this study was to review the outcome of patients who underwent surgery for treatment of cerebral metastatic melanoma. METHODS: A retrospective analysis was performed in 147 patients with cerebral metastases from melanoma who were treated surgically at a single institution between 1979 and 1999. Almost all patients underwent postoperative wholebrain radiation therapy. The mean patient age was 53 years (range 17-76 years); 69% of patients were male. A single cerebral metastasis was identified in 84% of patients, although 56% had synchronous extracranial metastases. The 30-day postoperative mortality rate was 2% and neurological symptoms resolved or improved in 78% of patients. Recurrence of intracerebral disease was seen in 55% of patients and 26% died of intracerebral metastases. Twenty-four patients underwent reoperation for recurrent cerebral disease. The median survival duration from the time of surgery for all patients was 8.5 months; the 3- and 5-year survival rates were 9% and 5%, respectively. Factors that significantly influenced survival on univariate analysis were the number of cerebral metastases (p = 0.015), a macroscopically complete excision (p < 0.05), and reoperation for recurrence (p = 0.02). The presence of extracranial metastases did not significantly influence survival. On multivariate analysis only the number of cerebral metastases significantly affected survival (p = 0.04). CONCLUSIONS: For the majority of patients with cerebral metastases from melanoma, surgery with adjuvant radiation therapy is a treatment option that improves neurological symptoms and produces minimal morbidity. Long-term survival (> 3 years) most likely occurs in patients with a single cerebral metastasis and no demonstrable extracranial disease. Reoperation for recurrent cerebral disease may be appropriate in selected cases.