Hayford, Kirsten M.

OBJECTIVE Schwannomas in the tibial, plantar, or medial calcaneal nerves around the ankle can mimic symptoms of tarsal tunnel syndrome. Outcomes after resection of schwannomas from these nerves have mainly been reported in case reports. The objectives of this study were to investigate the presentation and results for resection of schwannomas around the tarsal tunnel in a large case series and systematically review the currently available literature. METHODS Data from 40 patients (27 sporadic and 13 schwannomatosis cases) treated at 2 centers were retrospectively analyzed for preoperative type and duration of symptoms, schwannoma size at presentation, and outcome after resection. The following different locations around the ankle were compared: proximal to the tarsal tunnel (PTT), at the tarsal tunnel (ATT), and distal to the tarsal tunnel (DTT). The severity of symptoms was categorized in increasing order for pain only on touch, during load-bearing activities, and symptoms also at rest. Surgical outcome was assessed based on pain relief and occurrence of complications. The systematic literature review was performed using a PubMed and Embase search. RESULTS All but 1 patient presented with pain, local at the ankle, or neuropathic pain during weight-bearing activities (13/40, 32.5%). More than half of the patients also experienced symptoms at rest (52.5%). In 14 cases, the schwannoma was located PTT, in 17 cases ATT, and in 9 cases DTT in the plantar nerves. There were no significant differences in size and symptom duration at presentation for the different locations. Tumor size did not correlate with symptom severity. Outcomes after resection were excellent, with complete pain relief in all but 1 patient (97.0%). Complications included wound infection (5%) and temporary decreased sensation on the heel (7.5%). A review of 44 previously reported cases also frequently showed complete pain relief after resection. CONCLUSIONS The results of this study show that schwannomas around the tarsal tunnel often present with severe pain symptoms, even if the lesion is still relatively small. Resection frequently results in excellent pain relief. During surgery, it may not be necessary to open the entire length of the tarsal tunnel, thereby limiting the size of the incision, especially in schwannomas located proximally or distally to the tarsal tunnel.

OBJECTIVE Cervical dystonia (CD) is the most common focal dystonia, characterized by abnormal head postures and pain, often refractory to botulinum toxin therapy. Selective peripheral denervation (SPD) remains a key surgical option, but long-term outcomes in large cohorts are underreported. The purpose of this study was to evaluate the long-term outcomes of SPD in patients with botulinum toxin–refractory CD, focusing on symptom severity, pain, and head posture improvement. METHODS This retrospective study included 160 adults (mean ± SD age 54 ± 12.0 years, 46% male) with refractory CD who underwent SPD at a single center by a single surgeon from January 2005 to July 2023. Outcomes were assessed using subjective clinical measures and the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS), which was calculated retrospectively from clinical records. The modified Bertrand technique involved selective denervation and myotomies tailored to each patient’s dystonic pattern. TWSTRS scores were analyzed at baseline, 3 months, 1 year, and final follow-up (mean ± SD 10.3 ± 9.0 months). Time to minimal clinically important difference (MCID) (≥ 12-point TWSTRS drop) was evaluated with covariate-adjusted Kaplan-Meier modeling (ever vs never revised, evaluated with the log-rank test) and a counting-process Cox model with revision as a time-dependent covariate. RESULTS Among 160 patients (mean follow-up duration 21.6 ± 35.6 months), TWSTRS improved by 73.5% at 3 months and 61.3% at last follow-up (p < 0.001). Median time to MCID was 3.0 months for never revised patients versus 22.0 months for ever revised patients (log-rank chi-square statistic = 19.09, p < 0.0001). In a time-dependent Cox model, revision surgery was significantly associated with higher likelihood of achieving MCID (HR 2.31, p < 0.005). Pain relief and improved head posture were reported in over 50% of patients. Complications were minimal, and recurrence was observed in 4.2% of cases. Outcomes were consistent with or exceeded those reported in the literature with either SPD or deep brain stimulation (DBS). CONCLUSIONS SPD is an effective and durable surgical option for refractory CD, significantly improving pain, posture, and quality of life. Although revision surgery delayed time to improvement, it significantly increased the likelihood of achieving meaningful clinical improvement. Overall efficacy aligns with the existing literature, reinforcing its role as a first-line surgical intervention. Further studies should explore strategies to enhance long-term outcomes and delineate the role of SPD relative to DBS.

OBJECTIVE Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas predominantly associated with neurofibromatosis type 1 (NF1). However, their occurrence within NF type 2 (NF2)–related and SMARCB1-related schwannomatosis remains rare and poorly characterized. Accurate and timely diagnosis is challenging due to clinical and radiological similarities with benign schwannomas, potentially delaying appropriate management and impacting outcomes. This study presents an institutional case series aiming to better characterize the clinical presentations specifically for MPNSTs arising in patients with NF2- and SMARCB1-related schwannomatosis. METHODS This retrospective case series included patients diagnosed with schwannomatosis who subsequently developed histopathologically confirmed MPNSTs. Conducted at Mayo Clinic (Rochester, Minnesota) and University Health Network (Toronto, Canada), the study spanned January 1, 2003, to November 1, 2024. Patients were selected based on clinical or genetic diagnoses of schwannomatosis using International Consensus Group on Neurofibromatosis Diagnostic Criteria. Comprehensive clinical, radiological, and pathological data, including demographics, presenting symptoms, tumor features (size, location, immunohistochemistry, genetics), treatments (resection, chemotherapy, radiotherapy), and follow-up outcomes were extracted from electronic medical records. RESULTS The authors identified 8 patients with a mean age of 36 years, half of whom had NF2-related schwannomatosis. The most common presenting symptom was pain (71%). The mean tumor size was 8.2 ± 7.0 cm, with gross-total resection being the most common surgical treatment (67%), typically supplemented with radiation therapy (78%). More than half of the patients (56%) exhibited metastatic disease, and all tumors with reported grading were Fédération Nationale des Centres de Lutte Contre le Cancer grade 3. No tumors were associated with LZTR1 mutations. One notable case involved a 39-year-old male with SMARCB1-related schwannomatosis who had a femoral MPNST resected 13 years prior and subsequently developed a sciatic nerve MPNST that was managed successfully with neoadjuvant chemotherapy, radiation therapy, and negative margin resection. Of note, the second lesion arose from a hybrid neurofibroma/schwannoma. Another case, a 33-year-old male with SMARCB1-related schwannomatosis, had an incidental finding of epithelioid MPNST in a minimally symptomatic small palmar lesion. CONCLUSIONS This case series highlights that MPNSTs, although uncommon, can arise in NF2- and SMARCB1-related schwannomatosis without prior radiation exposure, presenting significant diagnostic challenges due to their similarity to benign schwannomas. The findings underscore the importance of maintaining clinical vigilance and employing individualized management strategies, balancing thorough resection with the preservation of function and patient quality of life.

OBJECTIVE Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas commonly associated with neurofibromatosis type 1 (NF1), whose occurrence in schwannomatosis remains poorly understood. This study aimed to characterize MPNSTs in NF type 2 (NF2)– and SMARCB1-related schwannomatosis through a systematic review and meta-analysis of survival outcomes. METHODS A comprehensive search of the PubMed, Embase, Scopus, SEER (Surveillance, Epidemiology, and End Results), and Web of Science databases was conducted from database inception through January 2024. Clinical, radiological, histopathological, and treatment data were extracted. Primary endpoints included overall survival (OS) and progression-free survival (PFS). Predictors of outcomes were analyzed using Kaplan-Meier survival curves and Cox proportional hazards models. RESULTS A total of 39 cases were identified. NF2-related disease accounted for 67% of cases, while 28% were SMARCB1 related. The mean age at MPNST diagnosis was 33 years (range 9–79 years). Pain (41%) and weakness (26%) were the most common presenting symptoms. The mortality rate was 72.9%. No tumors were associated with LZTR1 mutations. Tumor locations varied widely, with involvement of the pelvis, thigh, skull base, forearm/hand, and cranial nerves. Trends suggested improved survival in the absence of S100 loss, gross-total resection, and a known schwannoma precursor. Conversely, having an intracranial or intraspinal lesion or having NF2 in the setting of prior radiation therapy were found to be associated with decreased survival and increased progression. A risk stratification tool predicted OS (HR 28.0, p < 0.0001) and PFS (HR 12.1, p < 0.0001). CONCLUSIONS MPNSTs, although rare in schwannomatosis, can arise even in the absence of prior radiation exposure and may mimic benign schwannomas. A preliminary risk stratification tool may aid in identifying high-risk patients and optimizing treatment approaches, although validation is needed. Given the aggressive nature of MPNSTs and their potential for delayed diagnosis due to their rarity, vigilant monitoring and individualized treatment strategies are crucial. Future research should focus on refining risk prediction models and exploring targeted therapies for schwannomatosis-associated MPNSTs to improve patient outcomes.

OBJECTIVE Cervical dystonia (or spasmodic torticollis) is a neurological condition that results in abnormal movements and head posture, for which initial surgical intervention typically involves selective denervation of the sternocleidomastoid (SCM) and paraspinal muscles. However, muscle reactivation of the distal SCM stump can result in recurrent symptoms. In this study, the authors present their preliminary experience with distal SCM stump resection following selective denervation, with the aim of evaluating the effectiveness of the procedure and identifying patients who may benefit from this technique. METHODS This is a retrospective single-center cohort study of patients who underwent SCM stump resection as revision surgery for cervical dystonia. RESULTS A total of 18 patients (10 males [56%]) were included with a median (range) age of 54 (40–70) years. All patients received selective denervation of the SCM at the authors’ institution prior to SCM stump resection at a median (range) time of 12 (3–198) months between surgical procedures. At preoperative baseline, 13 patients (72%) possessed a rotational torticollis component to their head deviation, 12 (67%) possessed a laterocollis component, and 2 (11%) possessed a retrocollis component. At the most recent follow-up (median [range] 16 [4–119] months), 6 patients had complete resolution of their cervical dystonia (33%), while 10 had residual deviation (56%) and 2 had recurrent deviation (11%). However, compared to their post–selective denervation head position, 12 patients experienced improvement in their head position (67%), 4 patients had no change in their head position (22%), and 2 had worsening of their cervical dystonia (11%) following SCM stump resection. Importantly, 12 patients experienced improvement in their pain following SCM stump resection (67%). Patients who had a history of other movement/spasmodic disorders were more likely to have improvement in head position and improvement in pain after SCM stump resection, though neither of these results achieved statistical significance (p = 0.054). Additionally, patients who experienced full resolution of their cervical dystonia had shorter time between initial selective denervation surgery and SCM stump resection, though this result also did not achieve statistical significance (p = 0.068). CONCLUSIONS Distal SCM stump resection following selective denervation is a simple, safe, and effective option for many patients in treating refractory cervical dystonia. Patients with more severe preoperative presentations may experience greater benefit from SCM stump resection, though additional investigations are needed.

OBJECTIVE Resection of common peroneal nerve (CPN) schwannomas is generally believed to be associated with a high risk of postoperative deficit, especially the chance for development of a foot drop. The goal of this study was to investigate the surgical results for resection of schwannomas from the CPN around the knee and specifically the chance of developing a postoperative motor deficit. METHODS Data from 36 patients with sporadic schwannomas and 8 patients with schwannomatosis (12 schwannomas total) treated at two centers were retrospectively analyzed. For sporadic cases, different locations around the knee were compared (i.e., proximal to the fibular head [FH], at the FH, and distal to the FH), taking into account the preoperative duration of symptoms, size at presentation, and surgical results of resection. The literature was systematically reviewed for reported cases by searching the PubMed and Embase databases. RESULTS A total of 24 schwannomas proximal to the FH were surgically treated: 11 at the FH, and 13 distal to the FH. For the entire cohort, the mean size of CPN schwannomas distal to the FH at presentation was smaller (1.4 × 1.8 cm) compared with those proximal to (2.0 × 2.2 cm) and at (2.2 × 2.3 cm) the FH, although these differences were not statistically significant. The mean preoperative duration of symptoms was slightly longer for schwannomas distal to the FH (35 months) than for those proximal to the FH (21 months) and at the FH (27 months); however, this difference was not significant. Postoperative deficits occurred in 3 sporadic cases: 2 patients with temporary weakness (Medical Research Council grade 4) that completely resolved within several months and 1 patient who had previously undergone surgery elsewhere and presented with deficits and in whom weakness increased after resection. Improvement in preoperative deficits was observed in 1 patient with extensor hallucis longus muscle paralysis that completely recovered. One patient with schwannomatosis developed muscle weakness after resection of a plexiform schwannoma. A systematic review of 21 previously reported cases in the literature showed that larger CPN schwannomas (> 5 cm) were more likely to result in permanent motor deficits. CONCLUSIONS This retrospective study of 44 patients shows that peroneal nerve schwannomas around the knee can be safely removed with a low risk of deficits. The systematic review of the literature suggests that larger schwannomas are more likely to result in permanent deficit. In the authors’ opinion, CPN schwannomas can best be resected, preferably when the lesion is relatively small.

OBJECTIVE The formation and propagation of intraneural ganglion cysts (INGCs) is being elucidated by the unified articular theory. Its principles include a connection for joint fluid to egress from a synovial joint via an articular branch to a parent nerve and cyst following the path of least resistance, dependent on pressures and pressure fluxes. The occurrence of so-called extreme peroneal or tibial INGCs in the popliteal fossa extending to the sciatic nerve has been reported. One rarely described variant with a circumferential cyst within the subparaneurial compartment outside the epineurium of nerve(s) has been previously illustrated, but its mechanism and morphology have not been clarified. In this study, the authors aimed to investigate this type of cyst to challenge the principles of the unified articular theory. METHODS Four novel cases of patients with peroneal INGCs and "extreme subparaneurial cyst(s)" of the sciatic nerve and its distal branches were investigated: 3 arose from the superior tibiofibular joint (STFJ) and 1 from the knee joint. Three other cases of recognized extreme subparaneurial cyst (2 peroneal and 1 tibial from the STFJ) and 1 case of a peroneal subparaneurial cyst in the literature were reinterpreted. Data on clinical presentation, MR images, and surgical results were analyzed. RESULTS In all 8 cases, subparaneurial extension was observed to different degrees along the sciatic, tibial, common peroneal, sural, and deep and superficial peroneal nerves, as was subparaneurial-to-subparaneurial communication at the sciatic nerve bifurcation (i.e., crossover). Sequential MRI performed in 7 patients showed variable dynamic changes, including extreme ascent and descent. Extraneural rupture of the subparaneurial cyst, with spread into the surrounding tissue, was present at the sciatic nerve bifurcation in 6 cases. CONCLUSIONS The authors provide pathoanatomical and pathophysiological evidence supporting that extreme subparaneurial cysts follow the principles of the articular theory. They propose a distribution pattern that explains the occurrence and evolution of extreme subparaneurial cysts along the sciatic nerve and its distal branches in patients with peroneal or tibial INGCs and subepineurial cysts. Crossover in the subparaneurial compartment allows potentially extensive circumferential distribution within connected nerves. Also, dynamic factors can lead to dramatic changes in cyst size and appearance from reabsorption or extraneural rupture. In Part 2 of this study, the authors provide evidence showing that a fenestration in the epineurium allows cysts to pass from the subepineurial-to-subparaneurial, subparaneurial-to-subparaneurial, and subparaneurial-to-subepimyseal compartments.

OBJECTIVE Sciatic nerve injury following total hip arthroplasty (THA) predominantly affects the peroneal division of the sciatic nerve, often causing a foot drop. This can result from a focal etiology (hardware malposition, prominent screw, or postoperative hematoma) or nonfocal/traction injury. The objective of this study was to compare the clinicoradiological features and define the extent of nerve injury resulting from these two distinct mechanisms. METHODS Patients who developed a postoperative foot drop within 1 year after primary or revision THA with a confirmed proximal sciatic neuropathy based on MRI or electrodiagnostic studies were retrospectively reviewed. Patients were divided into two cohorts: group 1 (focal injury), including patients with an identifiable focal structural etiology, and group 2 (nonfocal injury), including patients with a presumed traction injury. Patient demographics, clinical examinations, subsequent surgeries, electrodiagnostic study results, and MRI abnormalities were noted. The Student t-test was used to compare time to onset of foot drop and time to secondary surgery. RESULTS Twenty-one patients, treated by one surgeon, met inclusion criteria (8 men and 13 women; 14 primary THAs and 7 revision THAs). Group 1 had a significantly longer time from THA to the onset of foot drop, with a mean of 2 months, compared with an immediate postoperative onset in group 2 (p = 0.02). Group 1 had a consistent pattern of localized focal nerve abnormality on imaging. In contrast, the majority of patients in group 2 (n = 11) had a long, continuous segment of abnormal size and signal intensity of the nerve, while the other 3 patients had a segment of less abnormal nerve in the midthigh on imaging. All patients with a long continuous lesion had Medical Research Council grade 0 dorsiflexion prior to secondary nerve surgeries compared with 1 of 3 patients with a more normal midsegment. CONCLUSIONS There are distinct clinicoradiological findings in patients with sciatic injuries resulting from a focal structural etiology versus a traction injury. While there are discrete localized changes in patients with a focal etiology, those with traction injuries demonstrate a diffuse zone of abnormality within the sciatic nerve. A proposed mechanism involves anatomical tether points of the nerve acting as points of origin and propagation for traction injuries, resulting in an immediate postoperative foot drop. In contrast, patients with a focal etiology have localized imaging findings but a highly variable time to the onset of foot drop.