Amrami, Kimberly K.

BACKGROUND The articular theory of the formation of intraneural cysts has significant supporting evidence at common locations but has been less accepted at rarer sites. There have been only 5 cases in the literature documenting an intraneural ganglion cyst in the dorsal cutaneous branch of the ulnar nerve (DCBUN), with only 1 case documenting a joint connection. In this report, the authors present a second case with a proven joint connection in support of the articular theory. OBSERVATIONS The authors report the case of a 73-year-old man who developed a large intraneural ganglion cyst within the DCBUN along the palmar ulnar aspect of his left wrist. Magnetic resonance imaging demonstrated an articular connection to the distal radioulnar joint. During surgery, the intraneural ganglion cyst was resected and the articular branch was disconnected. The patient recovered and returned to work 4 weeks postoperatively. LESSONS This case further supports the articular theory as the explanation for intraneural ganglion cysts, even at unusual locations. https://thejns.org/doi/10.3171/CASE24569

BACKGROUND The articular origin of intraneural ganglion cysts has been previously described and well supported, except for the median nerve at the level of the elbow. OBSERVATIONS The authors present a patient with a median intraneural ganglion cyst at the elbow region and magnetic resonance imaging (MRI) evidence of a joint connection to the proximal radioulnar joint. A 63-year-old man presented with thumb flexion weakness and dysesthesias in the thumb, index, and middle fingers. Electromyography confirmed a median nerve lesion at the elbow. MRI demonstrated a median intraneural cyst as well as an extraneural cyst, both arising from the proximal radioulnar joint. The articular branch between the cyst and the proximal radioulnar joint was identified preoperatively on MRI and intraoperatively using indocyanine green. Following disconnection of the articular branch and pedicle and decompression of the intra- and extraneural cysts, the patient recovered grade M4 motor function after 6 months, with resolution of neuropathic pain immediately after surgery. LESSONS The authors present the first case of a median intraneural cyst with a joint connection to the proximal radioulnar joint. The authors believe that this report along with other historical data strengthens the articular theory for intraneural ganglion cysts not only at this site but at all sites. https://thejns.org/doi/10.3171/CASE24564

Extremely severe nausea was experienced by four subjects positioned prone on a 7T scanner table with their arm extended overhead for a wrist examination and their head positioned approximately 10–20 cm above the magnet's central axis. Movement through the large static and spatial field gradients of current 7T MRI scanner magnets typically causes mild vestibular activation which is well tolerated by most individuals. However, when positioned off‐axis, the head moves through regions of even larger and more rapidly changing magnetic fields which in the current study were sufficient to induce the extremely severe nausea. Ensuring the head remains on‐axis mitigates this effect.

BACKGROUND The articular origin of intraneural cysts has been previously described and well supported. Intraneural ganglion cysts most commonly occur in adults and in the common peroneal nerve arising from the anterior aspect of the superior tibiofibular joint (STFJ). OBSERVATIONS The authors report a pediatric patient who developed a tibial intraneural cyst arising from the posterior aspect of the STFJ within months after surgical treatment of a peroneal intraneural cyst from the anterior aspect of the same joint. Surgery consisted of disconnecting the articular branch of the peroneal nerve and decompression of the cyst. Three-month postoperative magnetic resonance imaging showed resolution of the peroneal intraneural cyst and anterior compartment denervation but demonstrated a clinically occult small tibial intraneural ganglion cyst arising from the STFJ with popliteus muscle atrophy. LESSONS This case underscores the importance of addressing the underlying etiology (articular synovitis) or the communication pathways (articular branches) whenever feasible to mitigate intraneural cyst recurrence. Furthermore, this report reinforces the validity of the articular theory. https://thejns.org/doi/10.3171/CASE24277

Background: Diagnosis of foveal triangular fibrocartilage complex (TFCC) tears remains difficult. The purpose of this study was to evaluate whether dynamic computed tomography (CT) of the distal radioulnar joint (DRUJ) has a higher sensitivity in detecting foveal tears of the TFCC when compared with magnetic resonance imaging (MRI). Methods: A database query identified all patients above the age of 18 years with suspected foveal TFCC injuries who underwent bilateral dynamic CT imaging of the DRUJ, static 3T MRI, and subsequent wrist arthroscopy. All patients had evidence of foveal tenderness on clinical examination. The imaging results were validated with wrist arthroscopy. Results: Twelve patients with a mean age of 31 years (range, 18-53 years) were identified. Eight patients were diagnosed with a complete foveal detachment of the TFCC on wrist arthroscopy. Of the 8 patients with a foveal tear on DRUJ arthroscopy, only 3 had a preoperative physical examination suggestive of DRUJ instability. Magnetic resonance imaging identified foveal injuries in 4 of these 8 patients (sensitivity, 50%), and 3 of these were identified as only partial tears. Dynamic CT identified instability of DRUJ in 6 of 8 patients (sensitivity, 75%). Seven of 8 patients had imaging findings suggestive of a foveal tear when including either MRI or CT imaging (sensitivity, 88%). Of the 4 patients with an intact foveal attachment on arthroscopy, 3 (specificity, 75%) had a stable DRUJ on CT and all 4 (specificity, 100%) had an intact foveal attachment on MRI. Conclusion: Sixty-two percent of patients with foveal tears on arthroscopy have a stable DRUJ on clinical examination. When combining MRI and dynamic CT imaging of the DRUJ, the sensitivity of detecting a foveal TFCC tear approaches 88% compared with a gold standard of wrist arthroscopy.

BACKGROUND Lipomatosis of nerve (LN) is a rare disorder characterized by the massive enlargement of peripheral nerves, frequently accompanied by generalized fibroadipose proliferation and skeletal overgrowth. OBSERVATIONS The authors have been routinely following a 20-year-old male for lipomatosis of median nerve at the wrist noted shortly after birth. He had undergone resection of the lesion accompanied by sural nerve grafting at another institution. Clinically, although his neurological loss of function has been stable, he has had continued soft tissue growth. Serial magnetic resonance imaging has revealed persistent LN proximal to the repair sites with evidence of fatty proliferation in the sural grafts and continued LN and fatty proliferation distally. There has been a progressive circumferential pattern of fibrosis around the proximal and distal suture lines, which has a similar radiological pattern to desmoid type fibromatosis (a pattern recently described in neuromuscular choristoma [NMC] desmoid-type fibromatosis). LESSONS Considering the similar reaction of nerve in both LN and NMC despite differing genetic cascades, the authors believe a unifying process occurs in both lesions. The pattern of circumferential fibroproliferation would be most consistent with neuron-mediated growth from unspecified trophic factors, supporting a previously reported a nerve-derived “inside-out mechanism.” The clinical consequences of this unifying process are presented.