What is new in intraneural perineurioma?

Since the initial description of intraneural (IN) perineurioma in 1964, advances in the understanding of the clinical presentation, diagnostic imaging, pathologic features, and genetic underpinnings have changed how this pathology is managed. IN perineuriomas are rare, benign peripheral nerve sheath tumors, most frequently coming to clinical attention when patients present with painless, progressive weakness or sensory loss in adolescence or young adulthood. The gold standard of diagnosis has traditionally been with targeted tissue biopsy demonstrating "pseudo-onion bulb" formation with positive epithelial membrane antigen (EMA) staining. However, modern magnetic resonance imaging is allowing some patients to forgo biopsy. Recent genetic studies of IN perineuriomas have demonstrated common TRAF7 point mutations and rare NF2 mutations, which may present targets for diagnosis or therapy in the future. Current advances have allowed for us to provide improved patient counseling with informed understanding for various clinical scenarios. With the workup and diagnosis now clearly defined, the next frontier is for improving the lives of patients with IN perineuriomas through the interaction between restoration of functional deficits and advances in our understanding of the genetics of this entity.

Tibial intraneural ganglion cysts arising from the tibiofemoral joint: illustrative cases.

BACKGROUND: Intraneural cysts involving the tibial nerve in the knee region (popliteal fossa) are rare. According to the articular (synovial) theory, which posits a joint origin for this pathology, these cysts originate from either the superior tibiofibular joint (STFJ) or the tibiofemoral (knee) joint. As tibial intraneural cysts arising from the tibiofemoral joint remain poorly understood, the authors present 2 illustrative cases and a review of the world's literature on all tibial intraneural ganglion cysts in the knee region. OBSERVATIONS: Fourteen cases of tibial intraneural ganglion cysts arising from the tibiofemoral joint were identified in the literature. Different articular branch patterns were demonstrated, which could be explained by the varied, rich articular branch innervation at the knee. Favorable outcomes were observed in cases in which the articular branch had been disconnected and the cyst drained and were comparable to the outcomes seen in tibial intraneural ganglion cysts with an STFJ origin. LESSONS: Tibial intraneural cysts in the knee region can be subdivided by their joint of origin: the STFJ or the tibiofemoral joint. Those arising from the tibiofemoral joint originate from different areas of the joint and propagate in predictable patterns, with favorable outcomes following surgical intervention when the joint connection is identified and treated. The origin of tibial intraneural cysts from the tibiofemoral joint are more complex than those originating from the STFJ but seem to have similar propagation patterns and outcomes.

Posterior interosseous nerve paralysis secondary to an extraneural ganglion cyst from a radial neck pseudarthrosis: illustrative case.

BACKGROUND: Many benign and malignant tissue or bony lesions have been reported as causes of extrinsic or intrinsic posterior interosseous nerve (PIN) neuropathy at the proximal forearm/elbow region. The authors describe an unusual cause of external compression of the PIN due to a ganglion cyst arising from a radial neck pseudarthrosis (a false joint). OBSERVATIONS: Decompression of the PIN with the release of the arcade of Frohse was performed with resection of the radial head and the ganglion cyst. By 6 months postoperatively, the patient had a complete neurological recovery. LESSONS: This case illustrates a previously unreported cause of extraneural compression of the PIN from a pseudarthrosis. The mechanism for compression in this case from the radial head pseudarthrosis is likely attributable to the sandwich effect, in which the PIN is sandwiched between the arcade of Frohse at the supinator from above and the cyst below.

Perineurioma of the sciatic nerve with reticular, microcystic, and pseudolipoblastic features: illustrative case.

BACKGROUND: Perineuriomas are peripheral nerve sheath tumors that are composed of benign, localized proliferations of perineural cells and further subclassified as intraneural or extraneural (soft tissue) based on their relationship to the histological boundaries of the nerve. Multiple histological variants have been described, and herein the authors present the first known case of a pseudolipoblastic perineurioma affecting the nerve. OBSERVATIONS: A 52-year-old woman presented with a 5-year history of progressive, severe left buttock pain radiating down to the top of her foot and ankle, without any associated weakness, with a large mass in her sciatic nerve noted on magnetic resonance imaging (MRI). She underwent resection, which demonstrated a pseudolipoblastic perineurioma of the sciatic nerve, an unusual histological subtype composed of perineurial cells with an abundant clear intracytoplasmic background. Postoperatively, her pain resolved, and follow-up MRI showed no tumor persistence or recurrence. LESSONS: On imaging, this lesion had a benign appearance, with areas suggestive of subacute hemorrhage, and was associated with a nerve. Although the distinctive morphological features of this lesion may suggest liposarcoma, careful morphological evaluation and appropriate immunohistochemical studies allow its correct classification.

Sagittal Spinal Deformity in Patients with Idiopathic Normal Pressure Hydrocephalus.

AIM: To measure the baseline spinopelvic parameters and characterize the sagittal, and coronal plane deformities in patients with idiopathic normal pressure hydrocephalus (iNPH). MATERIAL AND METHODS: We analyzed a series of patients at one academic institution who underwent ventriculoperitoneal shunting for iNPH with pre-shunt standing full length x-rays. The series of patients was enrolled consecutively to minimize selection bias. We quantified comorbid sagittal plane spinal deformity based on the Scoliosis Research Society-Schwab classification system by assessing pelvic incidence and lumbar lordosis mismatch (PI-LL), pelvic tilt (PT), and sagittal vertical axis (SVA). RESULTS: Seventeen patients (59% male) were included in this study. Mean (± standard deviation) age was 74 ± 5.3 years with a body mass index (BMI) of 30 ± 4.5 kg/m < sup > 2< sup > . Six patients (35%) had marked sagittal plane spinal deformity by at least one parameter: five (29%) had greater than 20˚ PI-LL mismatch, three (18%) had > 9.5 cm SVA, and one (6%) had PT greater than 30˚. Additionally, the thoracic kyphosis exceeded the lumbar lordosis in nine patients (53%). CONCLUSION: Positive sagittal balance, with thoracic kyphosis exceeding lumbar lordosis, is common in iNPH patients. This may lead to postural instability, especially in patients whose gait does not improve following shunting. These patients may warrant further investigation and workup, including full length standing x-rays. Future studies should assess for improvement in the sagittal plane parameters following shunt placement.

Peroneal intraneural ganglion cyst with a nearly invisible joint connection (even to advocates of the articular theory): illustrative case.

BACKGROUND: The articular (synovial) theory describes the formation of intraneural ganglion cysts through defects in the capsule of synovial joints. While the articular theory is gaining significant traction in the literature, it is not universally accepted. Therefore, the authors present a case of a plainly visible peroneal intraneural cyst, although the subtle joint connection was not identified specifically at the time of surgery, with subsequent rapid extraneural cyst recurrence. The joint connection was not immediately evident on review of the magnetic resonance imaging, even to the authors who have a large experience with this clinical entity. The authors report this case to demonstrate that all intraneural ganglion cysts have joint connections, although they may be difficult to identify. OBSERVATIONS: An occult joint connection in the intraneural ganglion poses a unique diagnostic and management dilemma. High-resolution imaging is a valuable tool used to identify the articular branch joint connection as part of the surgical planning. LESSONS: Based on the articular theory, all intraneural ganglion cysts will have a joint connection through an articular branch, although this may be small or nearly invisible. Failure to appreciate this connection can lead to cyst recurrence. A high index of suspicion of the articular branch is needed for surgical planning.

Plexal intraneural perineurioma: an analysis of the clinicoradiologic presentation of this rare variant.

PURPOSE: Intraneural (IN) perineurioma is a rare benign peripheral nerve sheath tumor, typically presenting as a painless, progressive mononeuropathy in adolescents. A rare plexal variant has been described, although there are little data describing its clinicoradiologic features. Herein, we present the largest case series of plexal IN perineuriomas reported in the literature. METHODS: Electronic medical records (EMR) from 1990 to 2022 from a single academic institution were reviewed for a diagnosis of IN perineurioma involving the brachial or lumbosacral plexus. This identified 18 patients, of which 17 had available MR imaging. We reviewed the EMR for demographics, clinical presentation, imaging characteristics, and surgical outcomes. RESULTS: Eighteen patients were identified. Most patients were male (11/18, 61%) and first developed symptoms at the age of 9.6 years (range 7 months to 55 years). Diagnosis occurred on average at the age of 22 years (4-57 years), which is significantly earlier than distal IN perineurioma (p = 0.0096). All patients (100%, 17/17) presented with motor polyneuropathy and muscular atrophy in multiple nerve distributions, with associated sensory loss (12/17, 71%). Most plexal lesions occurred in the brachial plexus (66%, 12/18). Five (29%, 5/17) patients presented with a hand/foot discrepancy, and 5 patients (29%) had a limb length discrepancy. Five patients underwent tendon transfer, of which two had failure of tendon transfer at most recent follow-up (50%, 2/4) due to progression of neurologic loss affecting the donors. Of patients managed nonoperatively, 87% of patients (6/7) with follow-up information demonstrated disease progression with worsening motor function or sensory loss, and 2 patients demonstrated progression on imaging at most recent follow-up. CONCLUSIONS: Plexal perineurioma represents an uncommon variant of IN perineurioma that presents as a progressive motor and sensory polyneuropathy in childhood or early adolescence. Surgical management remains controversial, and tendon transfer tends to result in poor long-term surgical outcomes.

Prevalence of groin pain after primary dual-mobility total hip arthroplasty.

BACKGROUND: Instability remains a challenging problem following total hip arthroplasty (THA). Dual-mobility (DM) components are used with increasing frequency to mitigate this potential complication. As has been shown with larger metal-on-metal (MoM) THA, the larger size femoral head may pose an increased risk of groin pain. This study aims to evaluate the prevalence of groin pain following primary DM THA compared to other THA constructs. METHODS: We identified 190 primary THAs (183 patients) performed with DM components at a single academic institution from 2008 to 2017. We retrospectively reviewed standardised patient questionnaires and the electronic medical record to determine the prevalence of groin pain. DM patients were compared to historical controls of 39 MoM hip resurfacing, 26 large-head MoM THA, and 217 conventional THA. Mean age was 64 years, 58% were female, mean body mass index was 30 kg/m2, and mean follow-up was 3.5 years (range 2-8 years). RESULTS: The prevalence of groin pain in patients with DM components was 5%, similar to the prevalence reported by patients with conventional THA (7%). There was a decreased prevalence of groin pain in DM patients compared to hip resurfacing (18%) and MoM THA (15%). Among the 9 DM patients with groin pain, 1 was treated with iliopsoas injection, and 1 underwent radiofrequency ablation of the articular nerve. CONCLUSIONS: This study documents a relatively low prevalence of groin pain among primary DM THA patients. This is comparable with historical controls of conventional THA and decreased compared to hip resurfacing and large head MoM THA.

Hybrid tumors with perineurioma components: a systematic review of the literature and illustrative case.

PURPOSE: Hybrid peripheral nerve sheath tumors (HPNST) are a newly recognized class of peripheral nerve sheath tumor, composed of at least two areas characteristic of perineurioma, schwannoma, or neurofibroma. The literature consists only of case reports and small series; therefore, we present an illustrative case and an analysis of all reported cases of HPNST with a perineurioma component in the literature. METHODS: A systematic search of the literature was performed to identify all reported cases of hybrid perineurioma-schwannoma or perineurioma-neurofibroma in the world's literature. Individual cases were analyzed for demographics, clinical features, imaging, and outcomes. RESULTS: A total of 159 cases were identified across 41 studies. Hybrid tumors tended to present in mid-adulthood (median 38.5 years), predominantly affected females (57%, 89/156), as a painless (63%, 63/100) mass, or swelling. Ten patients (10/74, 14%) had a history of neurofibromatosis 1, and 2 patients a history of neurofibromatosis 2 (2/74, 3%). The majority (78%, 122/157) of cases occurred superficially, most commonly in the lower extremity (25%, 39/157). Perineurioma-schwannoma was the most reported (86%, 137/159) pathologic diagnosis, with 3 cases presenting with malignant features. Two cases reocurred after resection. CONCLUSION: HPNST tend to occur in mid-adulthood and present as slowly progressive, painless, superficial masses, with a heterogeneous appearance on imaging. These entities pose a unique diagnostic challenge and likely remain under-recognized in the literature and current clinical practice. They pose low risk of recurrence or malignant transformation, and future work regarding the association with neurofibromatosis and genetic profiles is needed.

The value of high-resolution imaging in an occult peroneal intraneural ganglion cyst: illustrative case.

BACKGROUND: Foot drop is a common complaint with a broad differential diagnosis making imaging a key part of the diagnostic workup. The authors present a patient with an occult peroneal intraneural ganglion cyst who underwent imaging with high-frequency ultrasound (US) and high-resolution magnetic resonance imaging (MRI) to highlight the role of such techniques in cases of peroneal neuropathy. OBSERVATIONS: Intraneural ganglion cysts are emerging as a common cause of common peroneal neuropathy. Imaging with US and MRI is a valuable tool used to illustrate the pertinent anatomy and identify the articular branch joint connection and cyst as part of the surgical planning and definitive management. LESSONS: Intraneural ganglion cysts can be small or nearly invisible and failure to appreciate the intraneural cyst can lead to symptom or cyst persistence or recurrence. High-resolution modalities can be useful in the diagnosis and surgical planning of difficult cases.

Reconstruction of Triangular Fibrocartilage Complex Avulsions (Palmar 1C) with Associated Lunotriquetral and Dorsal Capsule Injury: A Case Report.

CASE: A 34-year-old farmer and railroad worker injured his left wrist when working at a railroad. The resulting dorsal-ulnar wrist blow caused disabling pain. Splits and 2 subsequent surgeries failed, including an arthroscopic triangular fibrocartilage complex (TFCC) debridement and thermal ablation. Subsequently, magnetic resonance imaging documented a rare Palmer type 1C distal TFCC avulsion. Function was restored and return to farming permitted by reconstruction of the ulnotriquetral (UT) ligament using an extensor carpi ulnaris (ECU) slip. CONCLUSION: Chronic Palmer type 1C TFCC injuries can be successfully treated with ECU reconstruction of the UT ligament.

Preoperative Imaging of Intraneural Ganglion Cysts: A Critical Systematic Analysis of the World Literature.

BACKGROUND: Advancements in imaging and an understanding of the pathomechanism for intraneural ganglion cyst formation have led to increased awareness and recognition of this lesion. However, the precise role of imaging has been advocated for but not formally evaluated. METHODS: We performed a systematic review of the world literature to study the frequency of imaging used to diagnose intraneural ganglion cysts at different sites and compared trends in identifying joint connections. RESULTS: We identified 941 cases of intraneural ganglion cysts, of which 673 had published imaging. Magnetic resonance imaging (MRI, n = 527) and ultrasonography (US, n = 123) were the most commonly reported. They occurred most frequently in the common peroneal nerve (n = 570), followed by the ulnar nerve at the elbow (n = 88), and the tibial nerve at the ankle (n = 58). A joint connection was identified in 375 cases (48%), with 62% of MRIs showing a joint connection, followed by 16% on US, and 6% on computed tomography (CT). MRI was statistically more likely to identify a joint connection than was US (P < 0.01). In the last decade, joint connections have been identified with increasing frequency using preoperative imaging, with up to 75% of cases reporting joint connections. CONCLUSIONS: Preoperative imaging plays an important role in establishing the diagnosis of intraneural ganglion cyst as well as treatment planning. Imaging has proved superior to the sole reliance of operative exposure to identify a joint connection, which is necessary to treat the underlying disease. Failure to identify cyst connections on imaging can result in an inability to truly address the underlying pathoanatomy at the time of definitive surgery, leading to a risk for clinical recurrence. Therefore, management should be guided by an intersection between new knowledge presented in the literature, clinical expertise, and surgeon experience.

Does complete regression of intraneural ganglion cysts occur without surgery?

PURPOSE: The dynamic nature of intraneural ganglion cysts, including spontaneous expansion and regression, has been described. However, whether these cysts can regress completely in the absence of surgical management has important therapeutic implications. Therefore, we aim to review the literature for cyst regression without surgical intervention. METHODS: We reviewed our database of 970 intraneural ganglion cysts in the literature to search for evidence of complete regression based on strict radiologic confirmation, either spontaneously, or after percutaneous cyst aspiration or steroid injection. RESULTS: We did not find any examples of complete regression without surgical treatment that met inclusion criteria. Spontaneous regression was reported in four cases; however, only two cases had follow-up imaging, both of which demonstrated residual cysts. Nineteen cases of percutaneous intervention were found in the literature, 13 of which reported clinical improvement following aspiration/steroid injection; however, only seven cases had available imaging. Only two cases reported complete resolution of cyst on MR imaging at follow-up, but reinterpretation found residual intraneural cyst in both cases. CONCLUSION: We believe that pathology (structural abnormalities and/or increased joint fluid) always exists at the joint origin of intraneural ganglion cysts which persist even with regression of the cyst. The persistence of a capsular abnormality or defect can lead to recurrence of the cyst in the future, and while imaging may show dramatic decreases in cyst size, truly focused assessment of images will show a tiny focus of persistent intraneural cyst at the joint origin. Thus, expectant management or percutaneous intervention may lead to regression, but not complete resolution, of intraneural ganglion cysts.

Clinical and radiographic outcomes of hybrid glenoid fixation with a central porous titanium post: analysis of 713 consecutive shoulders.

BACKGROUND: Hybrid glenoid component fixation represents an emerging technology in total shoulder arthroplasty (TSA) design. However, there is a paucity of larger-scale studies reporting the outcomes following implantation of these components. This study aimed to determine the outcomes following primary TSA using hybrid glenoid component fixation with a central porous titanium post. METHODS: A retrospective review of 2 institutional databases identified patients aged ≥ 18 years who underwent primary elective hybrid TSA between 2009 and 2018 with a minimum of 2 years of follow-up. Outcomes evaluated included the visual analog scale pain score, range of motion, American Shoulder and Elbow Surgeons (ASES) score, complications, and implant survivorship free from reoperation or revision. Postoperative imaging was assessed for glenoid radiolucent lines and evidence of aseptic glenoid component loosening (AGL). RESULTS: A total of 713 shoulders in 666 patients with a mean age of 61 ± 6 years were included in the study at a mean follow-up period of 4.3 years (range, 2.0-9.1 years); male shoulders comprised 50.9% of shoulders. Notable clinical improvements were observed with respect to the visual analog scale pain score (7.0 to 1.4, P < .001), active forward elevation (91° to 155°, P < .001), active external rotation (21° to 50°, P < .001), and the ASES score (38.6 to 82.7, P < .001), with all exceeding the substantial clinical benefit threshold for TSA. The active internal rotation score also showed significant improvement (3.1 to 5.7, P < .001). Glenoid radiolucent lines were identified in 57 TSAs (8.2%), with 1 radiographically loose glenoid component (0.1%). There were 54 complications (7.6%), with postoperative rotator cuff tear as the most common complication (n = 15, 2.1%); only 4 cases (0.6%) of glenoid-related complications (AGL) were observed. The Kaplan-Meier rate of survival free from revision surgery was 98.7% at 1 year, 98.5% at 2 years, and 96.7% at 5 years. CONCLUSIONS: Hybrid glenoid component fixation of anatomic TSA with a central porous titanium post demonstrated statistically significant and clinically meaningful improvements in pain, range of motion, and ASES scores. Although AGL remains a concern, only 0.6% of TSAs sustained glenoid-related complications at a mean follow-up period of 4.3 years and the rate of survivorship free from revision was 96.7% at 5 years. These favorable clinical findings support the theoretical advantages of hybrid glenoid fixation; however, large comparative investigations with long-term follow-up are needed to validate these results.

Clinical Features, Natural History, and Outcomes of Intraneural Perineuriomas: A Systematic Review of the Literature.

BACKGROUND: Intraneural perineurioma is a rare peripheral nerve sheath tumor characterized by localized proliferation of perineurial cells. The literature consists predominantly of case reports and institutional series, with inconsistent and confusing nomenclature. We present a pooled analysis of all reported cases of intraneural perineurioma in the literature. METHODS: A systematic search of PubMed, MEDLINE, Embase, and Scopus was performed according to PRISMA guidelines to identify all reported cases of intraneural perineurioma in the literature. Individual cases were pooled and analyzed for demographics, clinical features, and outcomes. RESULTS: A total of 172 cases were identified across 72 studies, of which 149 were found in major peripheral nerves and their branches. Median age of patients at diagnosis and onset of symptoms was 18 years (interquartile range [IQR], 12-34 years) years and 13.5 years (IQR, 8-26 years), respectively, with 54.4% (81/149) being female. The most common sites were the sciatic nerve or its branches (41.9%), median nerve (13.5%), radial nerve (12.2%), and brachial plexus (12.2%). Most patients were managed conservatively (52.9%; 72/136). Among those managed conservatively with available follow-up (n = 31), median follow-up was 11 months, and most (67.7%, n = 21) reported no change in neurologic status, although worsening was noted in 29.0% (9/31). Among surgically managed cases (n = 64), the most common intervention was resection with or without repair (62.5%; 40/64), neurolysis (25%; 16/64), or tendon transfers without resection (12.5%; 8/64). No lesion recurred after surgical resection. CONCLUSIONS: Intraneural perineurioma represents a benign focal lesion presenting with weakness and atrophy affecting adolescents and young adults. Most cases are managed nonoperatively and surgical treatment strategies are varied.

High prevalence of cervical myelopathy in patients with idiopathic normal pressure hydrocephalus.

BACKGROUND: Both idiopathic normal pressure hydrocephalus (iNPH) and cervical myelopathy may result in progressive gait impairment. Some patients who do not respond to shunting despite a positive tap test may have gait dysfunction from cervical myelopathy. The objective of this study was to determine the prevalence of cervical myelopathy in patients with iNPH. METHODS: A consecutive series of patients undergoing shunt placement for iNPH were screened for cervical stenosis. Clinical manifestations of iNPH and cervical myelopathy, grade of cervical stenosis, cervical spine surgical intervention, timing of intervention, and outcomes were recorded. RESULTS: Fifty-two patients shunted for treatment of iNPH were included for analysis. 58 % were male with a mean age of 75.2 years (SD 7.3 years). All patients presented with gait disturbances. 39/52 (75 %) had cervical stenosis, and 9/52 (17.3 %) had significant (grade 2-3) cervical stenosis with myelopathy and were subsequently treated with surgical decompression. There was an association between increasing grade of stenosis and disproportionately enlarged subarachnoid space hydrocephalus (DESH). All patients with grade 2-3 cervical stenosis and symptoms of cervical myelopathy in addition to iNPH underwent cervical decompression surgery. CONCLUSIONS: Clinically significant cervical myelopathy was prevalent in patients with iNPH and was associated with increased rate of DESH, a finding that requires validation in a larger cohort. Based on these results, cervical imaging could be considered preoperatively in patients with iNPH, particularly when upper motor neuron findings are identified. Additionally, concomitant cervical stenosis should be ruled out in patients whose gait does not improve after shunt placement.

Limb Undergrowth in Intraneural Perineuriomas: An Under-Recognized Association.

BACKGROUND: Intraneural (IN) perineuriomas are a rare benign hypertrophic nerve tumor, most frequently occurring in young patients. Patients with IN perineurioma have been anecdotally found to have limb undergrowth; however, this has not been systematically evaluated. METHODS: Archived electronic records from 1990 to 2018 from a single institution were reviewed for pathology or radiology reports documenting a diagnosis of IN perineurioma. This identified 111 patients; 3 patients with IN perineurioma of cranial nerves were excluded. We further reviewed the 108 patients and identified those with a documented limb length discrepancy (LLD) or hand/foot size discrepancy (HFD) and tried to correlate findings with nerve-territory distribution. RESULTS: Twenty-seven (25.0%) patients had either LLD or HFD. Nine patients had only an LLD, 6 patients had only an HFD, and 12 patients had both. Patients with undergrowth were significantly younger at diagnosis than patients without (6.14 vs. 22.9 years, respectively). Although there was a trend toward a greater incidence of LLD in lower extremity IN perineuriomas, this was not statistically significant. Patients with proximal IN perineuriomas had a higher incidence of LLD or HFD than patients with distal IN perineuriomas. The difference between the 2 groups was statistically significant (P < 0.0001). All instances of undergrowth were explained by nerve-territory bone innervation. CONCLUSIONS: Limb undergrowth occurs in the affected nerve territory and is likely under-reported in patients with IN perineuriomas. Within our series, patients with documented LLD and HFD were likely to be significantly younger at diagnosis than patients without undergrowth.