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Open access

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

Karina A. Lenartowicz, Robert J. Spinner, Kimberly K. Amrami, and Shawn W. O’Driscoll

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.

Open access

Radial nerve myofibroma: a rare benign tumor with perineural infiltration. Illustrative case

Kitty Y. Wu, David J. Cook, Kimberly K. Amrami, and Robert J. Spinner

BACKGROUND

Myofibromas are benign mesenchymal tumors, classically presenting in infants and young children in the head and neck region. Perineural involvement, especially in peripheral nerves within the upper extremity, is extremely rare in myofibromas.

OBSERVATIONS

The authors present the case of a 16-year-old male with a 4-month history of an enlarging forearm mass and rapidly progressive dense motor weakness in wrist, finger, and thumb extension. Preoperative imaging and fine needle biopsy confirmed the diagnosis of a benign isolated myofibroma. Given the dense paralysis, operative management was indicated, and intraoperative exploration showed extensive involvement of tumor within the radial nerve. The infiltrated nerve segment was excised along with the tumor, and the resulting 5-cm nerve gap was reconstructed using autologous cabled grafts.

LESSONS

Perineural pseudoinvasion can be an extremely rare and atypical feature of nonmalignancies, resulting in dense motor weakness. Extensive nerve involvement may still necessitate nerve resection and reconstruction, despite the benign etiology of the lesion.

Open access

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

Karina A. Lenartowicz, Kimberly K. Amrami, Jorge Torres-Mora, and Robert J. Spinner

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.

Open access

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

Karina A. Lenartowicz, Kimberly K. Amrami, and Robert J. Spinner

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.

Open access

Unrecognized neuromuscular choristoma with recurrent desmoid-type fibromatosis and Marjolin ulcer: expanding the spectrum of neuromuscular choristoma sequelae within the nerve territory? Illustrative case

Andres A. Maldonado, Stephen M. Broski, Jodi M. Carter, and Robert J. Spinner

BACKGROUND

Neuromuscular choristoma (NMC) is a rare congenital lesion in which muscle tissue is admixed with nerve fascicles within a peripheral nerve. Patients commonly present in early childhood with neuropathy, plexopathy, or chronic undergrowth in the distribution of the affected nerve.

OBSERVATIONS

The authors present the case of a 35-year-old man with unrecognized neuromuscular NMC of the sciatic nerve, which resulted in recurrent, multicentric NMC-associated desmoid-type fibromatosis (NMC-DTF) within the nerve territory in association with a Marjolin ulcer, a cutaneous malignancy.

LESSONS

Based on anatomical and pathophysiological findings described in this case report, the authors support the association between NMC-DTF and Marjolin ulcer.

Open access

Occult lipomatosis of the nerve as part of macrodystrophia lipomatosa: illustrative case

Tomas Marek, Kimberly K. Amrami, and Robert J. Spinner

BACKGROUND

Macrodystrophia lipomatosa (MDL) is characterized by progressive overgrowth affecting soft tissues and bony structures and is part of lipomatous overgrowth syndromes. MDL has been associated with lipomatosis of the nerve (LN), an adipose lesion of nerve that has a pathognomonic magnetic resonance imaging (MRI) appearance as well as a mutation in the PIK3CA gene. The authors present a case of occult LN in the setting of MDL.

OBSERVATIONS

A 2-year-old boy with progressive soft tissue overgrowth of his proximal right lower extremity was initially diagnosed with neurofibromatosis type 1 (NF1). At our institution, NF1 as well as other overgrowth syndromes including PTEN hamartoma tumor syndrome were excluded. He was diagnosed as having so-called MDL. Upon reinterpretation of the patient’s MRI studies, short-segment LN involving the proximal sciatic nerve and part of lumbosacral plexus was identified. He underwent 2 debulking/liposuction procedures for soft tissue overgrowth. Genetic testing of tissue revealed a mutation in PIK3CA.

LESSONS

Thorough clinical examination (for signs of overgrowth) as well as an MRI study of the entire neural pathway is a critical part of the diagnostic workup to evaluate for LN. The authors believe that an increasing association of LN, even when occult, will emerge that will explain many cases with marked nerve-territory overgrowth.

Open access

Delayed motor weakness following peripheral nerve schwannoma resection: illustrative cases

Rohin Singh and Robert J. Spinner

BACKGROUND

Delayed facial palsy (DFP) after vestibular schwannoma resection is a well-documented, yet poorly understood condition. The exact pathophysiological mechanisms of DFP are unknown, although diminished intraoperative nerve response has been shown to be a prognostic factor. To date, no such condition has been described in regard to peripheral nerve schwannomas.

OBSERVATIONS

Here the authors present the first reported cases of delayed motor weakness (DMW) after peripheral schwannoma resection of the ulnar nerve at the elbow and peroneal nerve in the popliteal fossa. Both patients presented with a mass lesion and radiating paresthesias and had normal motor function preoperatively. Immediately after surgical resection, the patients had full strength. Within 24 hours, both patients exhibited marked weakness that gradually resolved over the course of several weeks.

LESSONS

DMW after peripheral schwannoma resection is a rare condition likely akin to delayed facial nerve palsy after VS resection. The mechanism of this phenomenon remains unknown, although symptoms appear to self-resolve with time. A better understanding of the processes driving this condition may allow for therapies that can expedite and improve long-term outcomes.

Open access

Selective denervation for cervical dystonia

Megan M. J. Bauman, Nikita Lakomkin, and Robert J. Spinner

Cervical dystonia (spasmodic torticollis) is a condition that involves sustained, involuntary contraction of neck and shoulder muscles, leading to abnormal movements and head posture. The authors present the case of a 41-year-old man with severe right rotational torticollis for 1.5 years due to predominant right cervical paraspinal and left sternocleidomastoid muscle hyperactivity. Following failed medical management, the patient elected to undergo surgical treatment for his torticollis. In their video, the authors discuss the steps of selective denervation using a modified Bertrand procedure, highlighting the associated anatomy and surgical planes. At the 1.5-year follow-up, the patient had no pain and his head position remained straight.

The video can be found here: https://stream.cadmore.media/r10.3171/2022.9.FOCVID2291

Open access

Angiosarcoma arising in a schwannoma of the peripheral nervous system: illustrative case

Nikita Lakomkin, Jorge Torres-Mora, Eric J. Dozois, and Robert J. Spinner

BACKGROUND

Schwannomas of the peripheral nerves are benign tumors that can very rarely undergo malignant transformation. These lesions are particularly challenging to diagnose via noninvasive techniques but can have significant implications for treatment.

OBSERVATIONS

This is a case of a 70-year-old female with a prior history of a right sciatic notch tumor that was diagnosed as a conventional schwannoma via histology from an initial biopsy and subsequent surgical debulking. Unfortunately, she experienced significant worsening of her motor deficit, whereby her postoperative foot weakness progressed to complete foot drop in less than 2 years. In addition, she demonstrated significant radiological progression, with more than 1 to 2 cm of growth in each dimension at her subsequent evaluation, along with intractable right leg pain. An additional operation was performed to completely remove the 7 × 8 cm tumor, and histology demonstrated angiosarcoma within a schwannoma. There was no evidence of recurrence at 15 months, and the patient had significant improvement in her pain.

LESSONS

Rapidly worsening function and radiological progression are not typically seen with conventional benign nerve sheath tumors and should prompt consideration of other lesions. Angiosarcoma within schwannoma is a rare pathology and optimal therapies for these tumors in terms of surgical timing and adjuvant therapy are still unknown.

Open access

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

Karina A. Lenartowicz, Kimberly K. Amrami, Jeffrey A. Strakowski, B. Matthew Howe, and Robert J. Spinner

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.