title: Post-surgical inflammatory neuropathy.
abstract: Post-surgical neuropathies are usually attributed to mechanical factors, such as compression, stretch, contusion or transection. The role of inflammatory mechanisms in neuropathies occurring after surgeries is poorly appreciated and not well characterized, and may provide a rationale for immunotherapy. A total of 23 selected patients with post-surgical neuropathies received nerve biopsies, of which 21 demonstrated increased inflammation. Here we report the clinical features in these 21 cases of biopsy-confirmed and 12 cases of clinically suspected post-surgical inflammatory neuropathies, in whom no trauma to the nerves was documented. All neuropathies developed within 30 days of a surgical procedure. Of 33 patients, 20 were male and the median age was 65 years (range 24-83). Surgical procedures were orthopaedic (n=14), abdominal/pelvic (n=12), thoracic (n=5) and dental (n=2). Patients developed focal (n=12), multifocal (n=14) or diffuse (n=7) neuropathies. Focal and multifocal neuropathies typically presented with acute pain and weakness, and focal neuropathies often mimicked mechanical aetiologies. Detailed analyses, including clinical characteristics, electrophysiology, imaging and peripheral nerve pathology, were performed. Electrophysiology showed axonal damage. Magnetic resonance imaging of roots, plexuses and peripheral nerves was performed in 22 patients, and all patients had abnormally increased T(2) nerve signal, with 20 exhibiting mild (n=7), moderate (n=12) or severe (n=1) enlargement. A total of 21 patients had abnormal nerve biopsies that showed increased epineurial perivascular lymphocytic inflammation (nine small, five moderate and seven large), with 15 diagnostic or suggestive of microvasculitis. Evidence of ischaemic nerve injury was seen in 19 biopsies. Seventeen biopsies had increased axonal degeneration suggesting active neuropathy. Seventeen biopsied patients were treated with immunotherapy. In 13 cases with longitudinal follow-up (median 9 months, range 3-71 months), the median neuropathy impairment score improved from 30 to 24 at the time of last evaluation (P=0.001).
  
  
  CONCLUSIONS
  (i) not all post-surgical neuropathies are mechanical, and inflammatory mechanisms can be causative, presenting as pain and weakness in a focal, multifocal or diffuse pattern; (ii) these inflammatory neuropathies may be recognized by their spatio-temporal separation from the site and time of surgery and by the characteristic magnetic resonance imaging features; (iii) occasionally post-surgical inflammatory and mechanical neuropathies are difficult to distinguish and nerve biopsy may be required to demonstrate an inflammatory mechanism, which in our cohort often, but not exclusively, exhibited pathological features of microvasculitis and ischaemia; and (iv) recognizing the role of inflammation in these patients' neuropathy led to rational immunotherapy, which may have resulted in the subsequent improvement of neurological symptoms and impairments.
authors.affiliation: Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
authors.forename: Nathan P
authors.initials: NP
authors.lastname: Staff
authors.forename: JaNean
authors.initials: J
authors.lastname: Engelstad
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Klein
authors.forename: Kimberly K
authors.initials: KK
authors.lastname: Amrami
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Spinner
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Dyck
authors.forename: Mark A
authors.initials: MA
authors.lastname: Warner
authors.forename: Mary E
authors.initials: ME
authors.lastname: Warner
authors.forename: P James B
authors.initials: PJ
authors.lastname: Dyck
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004594:Electrophysiology; D005260:Female; D006801:Humans; D007249:Inflammation / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009410:Nerve Degeneration / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D010525:Peripheral Nerves / Q000473:pathology* / Q000503:physiopathology; D010523:Peripheral Nervous System Diseases / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D013514:Surgical Procedures, Operative / Q000009:adverse effects*; D014657:Vasculitis / Q000473:pathology / Q000503:physiopathology