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The flexor digitorum accessorius longus muscle (ALM) can be overlooked as the eliciting factor in patients with tarsal tunnel syndrome (TTS), an entrapment neuropathy of the posterior tibial nerve that elicits sole numbness and pain. Most elicitations are idiopathic, however, mass lesions within the tarsal tunnel can be also implicated. We report an 80-year-old woman whose flexor digitorum ALM led to the onset of bilateral TTS. She had suffered numbness in both soles for 3 years. Magnetic resonance imaging (MRI) of the bilateral tarsal tunnel showed that the posterior tibial nerve was compressed by the arteriovenous complex and in contact with the flexor digitorum ALM. We diagnosed bilateral TTS based on her symptoms and imaging findings, and performed bilateral decompression surgery of the posterior tibial nerve under local anesthesia. The artery on both sides was dislocated for nerve decompression. Because the posterior tibial nerve on the right side was strongly compressed in ankle plantar flexion we excised a portion of the tendon compressing the nerve. Postoperatively her symptoms gradually improved and she reported surgical satisfaction 6 months after the operation. In patients with flexor digitorum ALM-related TTS, the effect of dynamic factors on MRI findings and on surgical treatment decisions must be considered. Intraoperatively, not only the flexor digitorum ALM, but also other potential etiologic factors eliciting TTS must be kept in mind., Competing Interests: The authors declare that they have no conflicts of interest in relation to our submitted manuscript and no commercial relationships or financial support from pharmaceutical or other companies. All authors are members of The Japan Neurosurgical Society (JNS) and have submitted signed, self-reported COI Disclosure Statement Forms available at the website for JNS members., (© 2024 The Japan Neurosurgical Society.)

Background: Tarsal tunnel syndrome (TTS) is a common entrapment neuropathy of the posterior tibial nerve. Surgery can be performed less invasively under local anesthesia. We adopted zig-zag skin incision to prevent postoperative wound complications., Methods: Between July 2022 and June 2023, we operated on 19 legs of 14 consecutive TTS patients (5 males, 11 females; average age 73.3 years). We made a 2- to 3-cm zig-zag skin incision on the tarsal tunnel. After posterior tibial nerve decompression by posterior tibial artery (PTA) transposition, the subcutaneous layer was tightly sutured with 4-0 PDS and the skin was closed with Dermabond Advanced. We investigated adverse events that developed during the first 30 postoperative days and recorded surgical outcomes at the final visit., Results: In all patients the nerves were successfully decompressed with PTA transposition. There were no intraoperative complications. During the 30 postoperative days there were no adverse events, including wound complications, and patients' symptoms improved significantly., Conclusion: Zig-zag skin incision was easy and convenient for surgical TTS treatment and may be useful for preventing postoperative wound complications.

Background: Superior/middle cluneal nerve entrapment (CN-E) is an elicitor of low back pain (LBP). The painDETECT questionnaire is used to characterize CN-E symptoms., Methods: Nineteen consecutive patients with LBP caused by CN-E (superior CN-E = 7; middle CN-E = 12) participated in a Japanese language painDETECT questionnaire survey before surgery. A score of 12 or lower was recorded as 'neuropathic component unlikely', a score of 19 or higher as 'neuropathic pain likely', and scores between 13 and 18 as 'neuropathic pain possible'. LBP severity was recorded on a numerical rating scale, the Roland-Morris Disability Questionnaire, and the EuroQol-5 dimension-5 level., Results: The mean painDETECT score was 11.8 and did not significantly differ between the superior CN-E and middle CN-E groups. We classified low back pain as unlikely to have a neuropathic component in 13 patients, as likely to have a neuropathic component in 2 patients, and as possibly neuropathic in 4 patients. There was no significant difference in the pain level of patients with scores of ≤12 and ≥13 on painDETECT. All patients reported trigger pain; the positive rate was high for electric shock pain, radiating pain, and pain attacks and low for a burning or tingling sensation, pain elicited by a light touch, and pain caused by cold or hot stimulation., Conclusion: The painDETECT questionnaire may not reliably identify LBP caused by superior/middle CN-E as neuropathic pain. A diagnosis of LBP due to CN-E must be made carefully because symptoms resemble nociceptive pain.

Background: Tarsal tunnel syndrome (TTS) is a common entrapment neuropathy that is sometimes elicited by ganglia in the tarsal tunnel., Methods: Between August 2020 and July 2022, we operated on 117 sides with TTS. This retrospective study examined data from 8 consecutive patients (8 sides: 5 men, 3 women; average age 67.8 years) with an extraneural ganglion in the tarsal tunnel. We investigated the clinical characteristics and surgical outcomes for these patients., Results: The mass was palpable through the skin in 1 patient, detected intraoperatively in 1 patient, and visualized on MRI scanning in the other 6 patients. Symptoms involved the medial plantar nerve area (n = 5), lateral plantar nerve area (n = 1), and medial and lateral plantar nerve areas (n = 2). The interval between symptom onset and surgery ranged from 4 to 168 months. Adhesion between large (≥20 mm) ganglia and surrounding tissue and nerves was observed intraoperatively in 4 patients. Of the 8 patients, 7 underwent total ganglion resection. There were no surgery-related complications. On their last postoperative visit, 3 patients with a duration of symptoms not exceeding 10 months reported favorable outcomes., Conclusions: Because ganglia eliciting TTS are often undetectable by skin palpation, imaging studies may be necessary. Early surgical intervention appears to yield favorable outcomes.

Objective: Common peroneal nerve (C-PN) entrapment neuropathy is the most common peripheral nerve neuropathy of the legs. C-PN decompression surgery is less invasive but may result in neurological complications. We report a rare case of nerve paralysis immediately after C-PN decompression surgery., Case Report: An 85-year-old man presented with leg numbness and pain. An electrophysical study revealed C-PN entrapment in the affected area and he underwent surgical decompression. Immediately after the procedure he complained of slight paralysis without pain (manual muscle test: 3/5), which gradually worsened and was complete at 60 min after surgery. We re-opened the skin incision 3 hours after the first operation and found that a subcutaneous suture had been applied to the connective tissue near the C-PN, resulting in marked compression of the nerve. After release of the suture his paralysis improved immediately. We confirmed that there was no other nerve compression and finished the operation. His paralysis disappeared completely., Conclusion: Peripheral nerve surgery, including C-PN decompression surgery, is less invasive, and the risk of complications is low. However, because the C-PN is located in the shallow layer under the skin, an excessively deep suture in the subcutaneous layer may compress the nerve and elicit nerve palsy. Therefore, careful postoperative follow-up is necessary because early decompression leads to good surgical results.

Objective: Meralgia paresthetica (MP) is an entrapment neuropathy of the lateral femoral cutaneous nerve (LFCN). We report a rare case of MP after microvascular decompression (MVD) surgery in the park-bench position in a patient with hemifacial spasm., Case: The patient was a nondiabetic 46-year-old woman (height: 155 cm, weight: 42 kg) who consumed alcohol infrequently. After a first MVD for right hemifacial spasm, the symptom recurred and she underwent a second MVD procedure in the park-bench position, after which hemifacial spasm resolved. However, she reported right anterolateral thigh pain and dysesthesia without motor weakness. The pain was limited to the LFCN area, and a pelvic compression test elicited a positive Tinel-like sign. Our preliminary diagnosis was MP. Because conservative therapy was ineffective, she underwent LFCN block 9 months after the second MVD procedure. Her pain improved dramatically and we made a definitive diagnosis of MP. There has been no recurrence after 30 months of observation, although she reported persistent mild dysesthesia in the LFCN area., Conclusion: MP is a rare complication after MVD surgery in the park-bench position. LFCN block can resolve symptoms and hasten diagnosis.

Carpal tunnel syndrome(CTS)is a common entrapment neuropathy caused by compression of the median nerve around the wrist. The risk factors of CTS include female sex, diabetes mellitus, hypothyroidism, obesity, arthritis, hemodialysis, acromegaly, and pregnancy. CTS is characterized by paresthesia in the distribution of the median nerve. Patients are often unaware of ring-finger splitting and the combination of Tinel's sign and Phalen's test improves diagnostic accuracy. In addition, electrophysiological assessments can help to confirm a CTS diagnosis; their sensitivity ranges from 57-94% and their specificity from 51-97%. CTS negatively affects the quality of life but improvement by surgery can be expected. For conservative treatment, a neutral wrist splint worn at night or oral medication such as nonsteroidal anti-inflammatory drugs, vitamin B12, and pregabalin have been shown to be effective against CTS. CTS surgery may be indicated in patients with thenar muscle atrophy and when conservative treatment is ineffective. The surgery involves a small skin incision under a microscope and local anesthesia. Long-term outcomes with respect to pain, numbness, function, symptomatology relapse, and frequency of re-surgery do not significantly differ between patients subjected to open or endoscopic surgery.

The clinical features and etiology of low back pain(LBP)and buttock pain(BuP)has been poorly understood. We report a case of long-term BuP that was successfully treated with gluteus medius muscle(GMeM)decompression under local anesthesia. A 71-year-old man was referred to our hospital because of long-term BuP and claudication. Left BuP that radiated to the left thigh was observed. The pain was mostly triggered by palpation at the middle of the iliac crest and greater trochanter. Lumbar and pelvic radiograms showed no significant lesions. Lumbar magnetic resonance imaging revealed a mild lumbar spinal canal stenosis at the L4/L5 segment. Based on the evidence of a trigger point and pain relieved after GMeM block injection, we made a diagnosis of GMeM pain. Although several GMeM block injections relieved his pain, the analgesic effect was transient and the claudication remained. Then, we decided to perform GMeM decompression. We made a 5-cm-long skin incision across the trigger point on the buttock. After confirming a wide exposure of the gluteal aponeurosis over the GMeM, we cut and opened it for sufficient GMeM decompression, and the GMeM expansion was confirmed. After surgery, his symptoms immediately improved. No evidence of recurrence was observed 6 months after his treatment. For the treatment of LBP and BuP, GMeM pain would be considered a causative factor. We report that it can be treated with a less invasive surgical technique, which would contribute to good clinical outcome.

Background: Tarsal tunnel syndrome(TTS)is an entrapment neuropathy of the posterior tibial nerve within the tarsal tunnel below the medial malleolus. An accurate diagnosis is difficult, and TTS is usually diagnosed from clinical symptoms due to the lack of accurate diagnostic tools. We aimed to standardize the diagnosis of TTS using MRI, and report the MRI conditions for clear visualization of the tarsal tunnel., Methods: We investigated which sequences and MRI conditions would be appropriate for the imaging of the tarsal tunnel in a healthy volunteer. As in routine brain MRI, the imaging time was within 15 minutes. We also performed an MRI study of the tarsal tunnel in two patients with TTS., Results: Axial images obtained by fat-suppression 3-dimensional T2 * -weighted imaging(3D-T2 * WI)are the most useful for visualization of the tarsal tunnel. The axial images obtained by T2-weighted imaging(T2WI)and T1-weighted imaging(T1WI)were also useful for visualization of the area around the flexor retinaculum. The appropriate slice thickness was determined to be 1.5 mm, based on the resolution and photographic time. The flip angle, necessary for tissue resolution, was set at 15° because it provided the clearest image and highest contrast between different tissues. The total photographic time was within 14 minutes, and it is acceptable for routine MRI studies of TTS. In the two cases of TTS included in this study, the tarsal tunnel was clearly visible., Conclusions: For diagnosis of TTS using MRI, axial images obtained by fat-suppression 3D-T2 * WI, 2-dimensional(2D)-T2WI, and 2D-T1WI are recommended. A coronal image obtained by reconstruction of fat-suppression 3D-T2 * WI might be useful for anatomical understanding. In future studies, we plan to evaluate patients with TTS using the above protocol.

A 60-year-old woman presented with a 1-year history of pain and numbness in the left anterolateral thigh. The symptoms aggravated on walking and standing. Her visual analogue scale(VAS)score was 7.1/10. Tinel's like sign was positive over the lateral femoral cutaneous nerve(LFCN), in the inguinal ligament region. LFCN block at the trigger point, in the inguinal ligament, resulted in relief of the symptoms and we diagnosed meralgia paresthetica(MP), which is the entrapment neuropathy of the LFCN. Initially, we performed observation therapy with oral medication and LFCN blocks. However, these treatments failed to relieve the symptoms. Therefore, we performed neurolysis with a microscope under local anesthesia. The symptoms improved immediately after surgery and her VAS score of thigh symptom improved from 7.1 to 1.9 after 3 months. Conservative and surgical treatment for MP generally yield good outcome and we should pay attention to the MP as a differential diagnosis for thigh numbness and pain.

Purpose: Many patients with diabetes mellitus (DM) experience numbness in the extremities. This DM neuropathy may be complicated by peripheral entrapment neuropathy. We prospectively investigated the cause(s) of limb numbness in DM patients., Materials and Methods: We enrolled 23 patients with uni- or bilateral limb numbness who were treated in our DM clinic. They were 10 men and 13 women; their average age was 63 years. The average duration of their neurological symptoms was 28.3 months., Results: Numbness was located in the upper limb in 7 patients, the lower limb in 11, and both the upper and lower limbs in 5. Among the 12 patients with upper-limb numbness, 9 manifested carpal tunnel syndrome and one each cervical OPLL or cervical spondylosis. Of the 16 cases of lower limb numbness, 10 were attributable to tarsal tunnel syndrome, 7 to lumbar spinal disease, 3 to restless leg syndrome, 2 to piriformis syndrome, and 1 to peroneal nerve entrapment neuropathy., Conclusions: In 21 of the 23 patients with uni- or bilateral limb numbness, the cause was attributable to several kinds of etiology such as entrapment neuropathy. Consequently, other treatable peripheral nerve disorders, e.g. tarsal tunnel syndrome, must be considered when diagnosing DM patients with limb numbness. Our findings suggest that therapeutic intervention to address such diseases will affect the quality of life of DM patients with limb numbness.