BACKGROUND: Although numerous articles have been published not only on the classification of thoracic outlet syndrome (TOS) but also on diagnostic standards, timing, and type of surgical intervention, there still remains some controversy because of the lack of level 1 evidence. So far, attempts to generate uniform reporting standards have not yielded conclusive results. OBJECTIVE: To systematically review the body of evidence and reach a consensus among neurosurgeons experienced in TOS regarding anatomy, diagnosis, and classification. METHODS: A systematic literature search on PubMed/MEDLINE was performed on February 13, 2021, yielding 2853 results. Abstracts were screened and classified. Recommendations were developed in a meeting held online on February 10, 2021, and refined according to the Delphi consensus method. RESULTS: Six randomized controlled trials (on surgical, conservative, and injection therapies), 4 “guideline” articles (on imaging and reporting standards), 5 observational studies (on diagnostics, hierarchic designs of physiotherapy vs surgery, and quality of life outcomes), and 6 meta-analyses were identified. The European Association of Neurosurgical Societies’ section of peripheral nerve surgery established 18 statements regarding anatomy, diagnosis, and classification of TOS with agreement levels of 98.4 % (±3.0). CONCLUSION: Because of the lack of level 1 evidence, consensus statements on anatomy, diagnosis, and classification of TOS from experts of the section of peripheral nerve surgery of the European Association of Neurosurgical Societies were developed with the Delphi method. Further work on reporting standards, prospective data collections, therapy, and long-term outcome is necessary.

Object: The authors report various techniques, and their results, after performing median and ulnar nerve transfers to reanimate the biceps muscle in C5–7 avulsion-related brachial plexus injuries (BPIs). Methods: Forty-three adult patients with BPIs of the upper-middle plexus underwent reinnervation of the biceps muscle; neurotization of the musculocutaneous nerve was performed using fascicles from the ulnar nerve (39 cases) and the median nerve (four cases). The different techniques included sectioning, rerouting, and direct suturing of the entire musculocutaneous nerve (35 cases); direct reinnervation of the motor branches of the musculocutaneous nerve (three cases); and reinnervation using small grafts to the motor fascicles that enter the biceps muscle (five cases). Elbow flexion recovery ranged from M2 to M4+, according to the patient's age and the level of integrity of the hand. No surgery-related failure occurred. No significant difference in outcome was related to any of the technical variants. In patients younger than age 45 years and exhibiting a normal hand function a score of M4 or better was always achieved. On average, reinnervation occurred 6 months after surgery. There was no clinical evidence of donor nerve dysfunction. Conclusions: When accurate selection criteria are met, the results after this type of neurotization have proved excellent.

✓ The aim of this paper was to report on further experience with a new technique for reanimation of the facial nerve. This procedure allows a straight end-to-side hypoglossal–facial anastomosis without interruption of the 12th cranial nerve or the need for graft interposition. It is technically demanding and time consuming but offers an effective, reliable, and extraordinarily quick means of reinnervating the facial muscles, including the orbicularis oculi muscle, thus avoiding the need for a gold weight in the eyelid or a fascial sling.

✓ Aggressive fibromatosis (desmoid tumor) of a peripheral nerve is a rarity. Isolated cases have been reported in which the tumor originated from neighboring structures and only secondarily invaded the nerves. The case described in this report is unusual because the tumor selectively invaded the patient's nerve fascicles, requiring removal and graft repair. The procedure was followed by an excellent clinical recovery and no recurrence as of the 6-year follow-up review.

Plexiform neurofibromas (Pnfs) are benign peripheral nerve sheath tumors that are major features of the human genetic syndrome, neurofibromatosis type 1 (NF1). Pnfs are derived from Schwann cells (SCs) undergoing loss of heterozygosity (LOH) at the NF1 locus in an NF1^+/− milieu and thus are variably lacking in the key Ras-controlling protein, neurofibromin (Nfn). As these SCs are embedded in a dense desmoplastic milieu of stromal cells and abnormal extracellular matrix (ECM), cell–cell cooperativity (CCC) and the molecular microenvironment play essential roles in Pnf progression towards a malignant peripheral nerve sheath tumor (MPNST). The complexity of Pnf biology makes treatment challenging. The only approved drug, the MEK inhibitor Selumetinib, displays a variable and partial therapeutic response. Here, we explored ECM contributions to the growth of cells lacking Nfn. In a 3D in vitro culture, NF1 loss sensitizes cells to signals from a Pnf-mimicking ECM through focal adhesion kinase (FAK) hyperactivation. This hyperactivation correlated with phosphorylation of the downstream effectors, Src, ERK, and AKT, and with colony formation. Expression of the GAP-related domain of Nfn only partially decreased activation of this signaling pathway and only slowed down 3D colony growth of cells lacking Nfn. However, combinatorial treatment with both the FAK inhibitor Defactinib (VS-6063) and Selumetinib (AZD6244) fully suppressed colony growth. These observations pave the way for a new combined therapeutic strategy simultaneously interfering with both intracellular signals and the interplay between the various tumor cells and the ECM.