Spinner, Robert J

BACKGROUND Cystic adventitial disease (CAD) and intraneural ganglion cysts (IGCs) are rare mucinous lesions typically linked to an articular origin via macroscopic conduits. While secondary propagation between vascular and neural systems may occur through shared fascial sheaths, a direct microvascular route has not been previously described. OBSERVATIONS A 60-year-old man presented with progressive left tibial neuropathy. High-resolution 7T MRI and surgery revealed a large popliteal CAD lesion connecting to the knee joint via the middle genicular artery, alongside a secondary tibial IGC lacking an independent articular nerve connection. Findings demonstrated that high-pressure CAD mucin tracked along a small connecting vascular branch, creating a novel microvascular arterio-neural pathway to infiltrate the tibial nerve. Targeted articular branch disconnection and cyst decompression yielded significant clinical improvement, with no recurrence on 7-month follow-up 7T MRI. LESSONS This case expands the unifying articular theory, demonstrating that synovial fluid propagation can exploit a microvascular arterio-neural pathway rather than strictly macroscopic fascial planes. High-resolution 7T MRI is essential for visualizing these subtle connections. Successful management requires meticulous identification and disconnection of the primary joint connection to prevent recurrence. https://thejns.org/doi/10.3171/CASE26411

BACKGROUND Differential awakening is a well-known, yet poorly understood phenomenon seen in patients with intracranial pathologies. Because acute postoperative neurological decline has many potentially reversible causes, distinguishing differential awakening from other etiologies is critical. To the authors’ knowledge, differential awakening has not been reported following peripheral nerve procedures. OBSERVATIONS A 40-year-old man presented with a 1.5-year history of painful bilateral cervical and right lumbosacral radiculoplexus neuropathy recently associated with bilateral facial and vestibulocochlear neuropathy. He had not responded to treatment trials. A sciatic nerve lesion in the sciatic notch was identified on imaging and an open biopsy of the posterior femoral cutaneous nerve was pursued. Immediately after emergence from anesthesia, he demonstrated a complete inability to dorsiflex or plantar flex the right foot, despite minimal intraoperative manipulation of the sciatic nerve. Over the ensuing hour, motor function progressively returned to baseline. The transient postoperative motor deficit was attributed to differential awakening of the sciatic nerve. Pathological analysis confirmed high-grade B-cell lymphoma. LESSONS Differential awakening may be an underrecognized cause of transient neurological worsening during emergence from anesthesia following peripheral nerve surgery. Further investigation is needed to clarify the underlying mechanisms and define its incidence and risk factors. https://thejns.org/doi/10.3171/CASE251028

BACKGROUND Perineural spread (PNS) of colorectal carcinoma (CRC) is a rare and challenging diagnosis. Its clinical and radiological presentation is often subtle and can overlap with radiation-induced neuropathy and malignant nerve tumors, complicating timely diagnosis. The role of circulating tumor DNA (ctDNA) in the detection of PNS has not been previously described. OBSERVATIONS A 48-year-old man with a history of rectal cancer and perineural invasion presented with progressive, refractory sciatic neuropathic pain. Conventional surveillance imaging was initially negative despite subtle rising of carcinoembryonic antigen and ctDNA levels. Subsequent MRI revealed abnormalities of the lumbosacral plexus and sciatic nerve, and fascicular biopsy confirmed metastatic CRC involving the sciatic nerve, establishing the diagnosis of PNS. LESSONS This case highlights PNS as a rare but important consideration in patients with focal neuropathic symptoms and prior CRC. Circulating tumor DNA positivity may serve as an early indicator of occult tumor activity even within the nerves when imaging is equivocal. However, currently histopathological confirmation remains the only definitive method to distinguish PNS from alternative diagnoses and is essential to guide appropriate management. https://thejns.org/doi/10.3171/CASE25997

BACKGROUND Bertolotti syndrome is an underrecognized cause of chronic low back pain. Back pain generated from Bertolotti syndrome is believed to result from altered weight dissipation mechanics and/or instability of the pseudoarticulation, while local nerve root compression may result in radiculopathy. Here, the authors describe the findings of a patient with treatment-refractory low back pain found to have a cystic lesion arising from a Bertolotti joint causing L5 nerve root compression. To their knowledge, this has not been previously described in the literature. OBSERVATIONS Despite early recognition of Bertolotti syndrome, the patient’s back pain remained resistant to many years of both conservative and surgical management. The novel finding of a cyst arising from the pseudoarticulation complicated the management. The patient is scheduled to undergo further surgery this year. LESSONS This case highlights a pseudocyst associated with a Bertolotti joint. The cyst introduced additional clinical uncertainty to what is already an uncommon and difficult to treat condition. Resection of the Bertolotti joint failed to improve the patient’s symptoms. Postoperatively, a complex hemorrhagic pseudocyst was seen on imaging, possibly due to the pseudoarticulation with persistent motion. Ongoing efforts to characterize Bertolotti syndrome and its associated imaging findings are necessary to better optimize management strategies in these patients. https://thejns.org/doi/10.3171/CASE25948

BACKGROUND Intraneural ganglion cysts (IGCs) are mucinous lesions that originate from adjacent synovial joints. According to the articular theory, synovial fluid tracks from a joint into the parent nerve through an articular branch. In uncommon sites such as the sural nerve, this connection can be difficult to identify. This report illustrates the use of a preoperative intra-articular fluorescein injection as a tool to identify the articular branch during surgery. OBSERVATIONS A 60-year-old woman presented with lateral foot pain, numbness, and a palpable mass along the left sural distribution. MRI showed a large cyst extending along the course of the sural nerve with connection to the subtalar joint. Fluorescein was injected preoperatively into this joint to detect the articular branch intraoperatively with ultraviolet illumination. The connection was transected at the joint origin, and the cyst was decompressed, preserving the parent nerve. Postoperatively, the patient had complete pain relief and sensory recovery, and MRI at 3 and 8 months confirmed resolution of the cyst. LESSONS Sural IGCs conform to the articular theory and can be managed effectively by transection of the articular branch. Preoperative intra-articular fluorescein injection is a useful tool to detect the articular branch that can be difficult to find in sural IGCs. https://thejns.org/doi/10.3171/CASE251018

ABSTRACT The paraneurium is a distinct connective tissue sheath that loosely envelopes the epineurium. The space between the para‐ and epineurium (the subparaneurial compartment) holds significant clinical relevance, serving as a target for deposition of regional anesthesia and a potential pathway for the pathological spread of cysts and tumors. However, visualization of the paraneurial layer, as a separate structure from the epineurium, remains challenging with conventional MRI, especially in the absence of pathology. This study evaluated the visualization of the paraneurium using ultra‐high‐field 7‐Tesla (7 T) MRI compared to conventional field strengths. We assessed normal nerve anatomy and a spectrum of pathological cases, including intraneural ganglion cysts, schwannomas, intraneural perineuriomas, and metastatic melanoma. The results demonstrated that 7 T MRI provides superior resolution and delineation of the paraneurium compared to 1.5 and 3 T systems. In normal anatomy, T1‐weighted and proton density (PD) sequences provided optimal contrast between the paraneurium and surrounding adipose tissue. In contrast, for pathological cases, T2‐weighted sequences with fat suppression were superior for depicting the paraneurium and identifying subparaneurial involvement. In conclusion, 7 T MRI offers a significant advantage in identifying the thin paraneurial layer. This capability provides valuable insights into the pathogenesis of tumor spread and holds promise for improving pre‐operative planning and clinical decision‐making in peripheral nerve pathology.

BACKGROUND Ulnar neuropathy at Guyon’s canal is rare, but when it occurs, it is frequently due to underlying masses, including extraneural and intraneural ganglion cysts, as well as adventitial cysts. The pathogenesis of these cysts, especially at a rare site, remains controversial. The articular theory, which is gaining popularity, posits that a joint connection via a nerve (or vascular) branch to a neighboring joint represents the pathway for their formation and propagation. OBSERVATIONS A recently published case of a patient with an ulnar intraneural ganglion at the wrist with a series of postoperative cystic recurrences was reevaluated, as it challenged the articular theory. No discrete articular branch had been identified on imaging or at surgery. Serial MR images were reinterpreted, which revealed that the original intraneural cyst was treated; new sequential cysts—an adventitial cyst and then a soft tissue ganglion—developed, all arising from the same wrist joint. LESSONS This case strengthens the principles of the articular theory for intraneural ganglion, adventitial, and soft tissue ganglion cysts. A small wrist connection from the ulnar intraneural ganglion was unrecognized and untreated. Scarring disrupted the original nerve pathway and pressure dynamics. New cysts developed through neighboring joint capsular rents along different pathways into other “compartments” (vessel or soft tissues). https://thejns.org/doi/10.3171/CASE25618

BACKGROUND Recently, the distribution of subparaneurial ganglion cysts involving the common peroneal and tibial nerves was described based on MRI analysis. Crossover in extreme cases was observed at the sciatic bifurcation through a mechanism comparable to a geyser, enabled by fenestrations in the epi- and paraneurium at the level of the bifurcation. The goal of this study was to investigate whether the geyser theory for crossover holds for other locations. OBSERVATIONS The authors’ prospectively maintained database of > 1100 cases of intraneural ganglion cysts in the world’s literature was queried for the existence of subparaneurial ganglion cysts at locations other than the knee. A previously unrecognized case involving the ulnar nerve originating from the elbow joint was found. Reinterpretation of the patient’s MRI studies showed circumferential subparaneurial distribution of a cyst over a long distance. Based on their previously reported geyser theory, the authors wondered if crossover had occurred at the level of the medial cord. A fenestration in the epi- and paraneurium at this level was confirmed on histological analysis of a normal cadaveric specimen. LESSONS This illustrative case shows that the geyser theory also holds in other locations. Surgical treatment of these subparaneurial cysts still follows the principles of the unified articular theory. https://thejns.org/doi/10.3171/CASE25671

ABSTRACT At the 42nd Annual Meeting of the American Association of Clinical Anatomists (AACA) in Bellevue, Washington, June 2025, two inaugural events—the Clinical Anatomy Fireside Chat (CAFC) and the Clinical Anatomy Symposium: Head and Neck 2025 (CAS)—fostered rich dialogue on the evolving role and operational definition of clinical anatomy. Experts from various clinical and anatomical disciplines explored the meaning of clinical anatomy, highlighting the absence of a universal definition despite its frequent use in education and research. Through these interdisciplinary discussions, a consensus emerged: clinical anatomy is not defined solely by the possession of clinical credentials but by the integration of anatomical knowledge and clinical relevance, achieved most effectively through collaboration. Clinical anatomy education and research require different depths of clinical knowledge depending on the audience and objective, and meaningful collaboration can bridge gaps in expertise. The symposium further illustrated that high‐quality clinical anatomy emerges from mutual respect and reciprocal insight between clinicians and anatomists. This article presents a consensus statement developed by AACA representatives and invited speakers, affirming that collaboration is not only foundational to the practice of clinical anatomy but also fundamental to its definition. These conclusions aim to guide future educational models, research strategies, and interdisciplinary partnerships in the field of clinical anatomy.