Novel imaging techniques using 18 F-florbetapir PET/MRI can guide fascicular nerve biopsy in amyloid multiple mononeuropathy.

BACKGROUND: Multiple mononeuropathy is a rare presentation of primary (AL) amyloidosis and nerve biopsy is usually needed for diagnosis. Conventional imaging is useful to identify proximal nerve involvement but may be inadequate. We report a patient with multiple mononeuropathy whose presentation was suggestive of AL amyloid neuropathy and in whom repeated tissue biopsies were negative for amyloid (including two sensory nerves and one muscle). METHODS: The patient underwent magnetic resonance imaging (MRI) and whole body 18 F-florbetapir positron emission tomography (PET)/MRI. RESULTS: Whole body 18 F-florbetapir PET/MRI revealed abnormal low-level florbetapir uptake in the right proximal tibial and peroneal nerves, which provided a target for a sciatic bifurcation fascicular nerve biopsy that was diagnostic of AL amyloidosis. CONCLUSIONS: 18 F-florbetapir PET/MRI imaging is a promising diagnostic tool for patients with suspected peripheral nerve amyloidosis (including multiple mononeuropathy) in whom conventional imaging and nerve and muscle biopsies miss the pathology.

Expanded teased nerve fibre pathological conditions in disease association.

OBJECTIVE: To describe an expanded teased nerve fibre classification in disease association. METHODS: We reviewed four newly proposed teased nerve fibre types (Types J-M): Type J, rope-like fibres; K, fibril-like clumps of osmium positivity; L, cellular debris along and within nerve fibres; M, circular axonal inclusions surrounded by thin myelin. Different clinical pathological entities were studied for these fibre types including chronic inflammatory demyelinating polyradiculoneuropathy (CIDP: N=20); amyloid polyneuropathy (N=20); intraneural B-cell lymphoma (N=20) or adult-onset polyglucosan body disease (APBD: N=6) in comparison with 112 disease controls. Student's t-test was used to test significance of association between the identified fibre types and the specific clinical diagnosis. RESULTS: Each fibre type significantly associated (p<0.001) with particular disease categories: Type J, 60% of CIDP cases; Type K, 75% of amyloid cases; Type L, 75% of intraneural lymphoma cases; Type M, 100% of APBD cases. Rarely were these fibres found in the other disease control cases ≤3% of cases. In three cases, the teased fibre findings were so striking additional paraffin nerve preparations were made to make the pathological diagnosis when initial paraffin sections were non-diagnostic. CONCLUSIONS: Teased nerve fibre Types J-M associate with commonly seen pathological diagnosis and are helpful in the consideration of specific neuropathy diagnoses.

Onion-bulb patterns predict acquired or inherited demyelinating polyneuropathy.

INTRODUCTION: Onion-bulbs (OB) are concentrically layered Schwann-cell processes, surrounding nerve fibers, occurring in both inherited and acquired demyelinating polyneuropathies. We investigated whether OB patterns (generalized, mixed, or focal) correlate with acquired or inherited neuropathies. METHODS: One hundred thirty-one OB-rich nerve biopsies were graded for OB pattern and inflammation without knowledge of clinical history. We classified inherited (n = 49) or acquired (n = 82) neuropathies based solely on clinical history. RESULTS: Fifty-one biopsies had generalized (34 inherited vs. 17 acquired, P < 0.001), 54 mixed (48 acquired vs. 6 inherited, P < 0.001), and 26 focal/multifocal (inherited [n = 9], acquired [n = 17]) OB. Inflammation occurred more frequently in acquired (n = 54) than inherited (n = 14) neuropathy (P = 0.004). DISCUSSION: Generalized OB correlates with inherited neuropathy; mixed OB with acquired. Inflammation occurs more in acquired neuropathy cases. OB patterns are best explained by ubiquitous Schwann-cell involvement in inherited and multifocal Schwann-cell involvement in acquired neuropathies and predict the electrophysiology of uniform demyelination in inherited and unequal demyelination in acquired neuropathies. Muscle Nerve 59:665-670, 2019.

Somatotopic heat pain thresholds and intraepidermal nerve fibers in health.

INTRODUCTION: For sequential and somatotopic assessment of small fiber neuropathy, heat pain (HP) tests of hypoalgesia might be used instead of decreased counts of epidermal nerve fibers (ENFs), but then healthy subject reference values of HP thresholds are needed. METHODS: Using the Computer Assisted Sensation Evaluator IVc system, HP thresholds of hypoalgesia were estimated for 10 unilateral sites and counts of ENFs for 4 of them in healthy subjects. RESULTS: In healthy subjects, small but statistically significant differences of both HP thresholds of hypoalgesia and counts of ENFs were observed among tested sites. Significant correlations between HP thresholds and counts of ENFs were not found. DISCUSSION: For the studied somatotopic sites, we provide ≥95th and ≥99th percentile reference limits for HP 0.5 and 5 of 1-10 HP thresholds of hypoalgesia and decreased counts of ENFs at ≤5th and ≤1st percentile levels. Muscle Nerve 58: 509-516, 2018.

Clinical-pathologic correlations in voltage-gated Kv1 potassium channel complex-subtyped autoimmune painful polyneuropathy.

INTRODUCTION: Voltage-gated Kv1 potassium channel complex (VGKC) autoantibodies subtyped for leucine-rich glioma-inactivated 1 (LGI1), contactin-associated-proteinlike 2 (CASPR2), and Kv IgGs have a spectrum of neurological presentations. Painful polyneuropathy is seen in some patients, but nerve pathology descriptions are lacking. METHODS: Clinicopathologic features were studied in subtyped VGKC-autoantibody-seropositive patients who had undergone nerve biopsies. RESULTS: Five patients were identified, 1 LGI1 IgG positive and 1 CASPR2 IgG positive, but all negative for Kv1.1-, 1.2-, 1.6-subtyped IgG autoantibodies. Median symptom duration was 17 months. Pain was the predominant symptom; 3 had mild sensory loss and/or weakness. Histopathological abnormalities were limited to axonal loss in 3. None had mononuclear cellular infiltrates. Electron micrographs revealed no interstitial abnormalities. Three patients reported marked improvement in pain with immunotherapy. CONCLUSIONS: The nerve biopsy histopathology of patients subtyped for LGI1 and CASPR2 IgGs within the VGKC-complex spectrum disorders shows either normal density or axonal fiber loss without inflammatory infiltrates. A reversible neural hyperexcitable mechanism is considered to be the cause of this painful polyneuropathy. Muscle Nerve 55: 520-525, 2017.

Immunotherapy-responsive allodynia due to distal acquired demyelinating symmetric (DADS) neuropathy.

INTRODUCTION: Distal acquired demyelinating symmetric (DADS) neuropathy is a distal variant of chronic inflammatory demyelinating polyradiculoneuropathy. It is characterized by chronic distal symmetric sensory or sensorimotor deficits. Sensory ataxia is a common clinical presentation. Nerve conduction studies typically show markedly prolonged distal motor latencies. METHODS: We report 2 patients with chronic progressive generalized pain and fatigue, with normal neurological examinations except for allodynia. RESULTS: Nerve conduction studies were typical of DADS neuropathy. Monoclonal protein studies were negative. Cerebrospinal fluid protein levels were elevated. Sural nerve biopsies revealed segmental demyelination and remyelination. One biopsy had marked endoneurial and epineurial lymphocytic infiltration. Immunomodulatory therapy alleviated the pain and fatigue and markedly improved distal motor latencies in both patients. CONCLUSIONS: DADS neuropathy can present with pain and a normal neurological examination apart from allodynia. Nerve conduction studies are necessary for diagnosis. These patients respond to immunotherapy better than typical DADS neuropathy patients with sensory ataxia. Muscle Nerve 54: 973-977, 2016.

Progressive polyradiculoneuropathy due to intraneural oxalate deposition in type 1 primary hyperoxaluria.

INTRODUCTION: A 24-year-old man with primary hyperoxaluria type 1 (PH1) presented with a rapidly progressive axonal and demyelinating sensorimotor polyradiculoneuropathy shortly after the onset of end-stage renal disease. His plasma oxalate level was markedly elevated at 107 µmol/L (normal<1.8 µmol/L). METHODS: A sural nerve biopsy was performed. Teased fiber and paraffin and epoxy sections were done and morphometric procedures were performed on this sample and on an archived sample from a 22-year-old man as an age- and gender-matched control. Embedded teased fiber electron microscopy was also performed. RESULTS: The biopsy revealed secondary demyelination and axonal degeneration. Under polarized light, multiple bright hexagonal, rectangular, and starburst inclusions, typical of calcium oxalate monohydrate crystals, were seen. CONCLUSIONS: The proposed mechanisms of nerve damage include disruption of axonal transport due to crystal deposition, toxic effect of oxalate, or nerve ischemia related to vessel occlusion from oxalate crystal deposition.

Immune-mediated neuropathies following stem cell transplantation.

OBJECTIVE: To study the clinical, electrophysiological and pathological characteristics and outcome of immune-mediated neuropathy (IMN) following stem cell transplantation (SCT). METHODS: Retrospective chart review of the Mayo Clinic Rochester SCT database between January 1997 and August 2012. RESULTS: Of the 3305 patients who underwent SCT, 12 patients (0.36%) had IMN. The median time from SCT to IMN was 7 months. IMN typically presented as an asymmetric radiculoplexus neuropathy (7/12 patients) or acute polyradiculoneuropathy (Guillain-Barré syndrome) (4/12). Neurophysiology showed demyelinating neuropathy in four patients and axonal neuropathy in eight. Cerebrospinal fluid protein was increased in five of six patients (median 67 mg/dL). The Neuropathy Impairment Score (NIS) improved in all patients (mean NIS 43-10, p=0.016). Six patients died. One patient died from complications of IMN and one died from complications of the haematological disease. Five patients had recurrence of their malignancy within 4 months of the IMN and of these, four died. CONCLUSIONS: IMN occurs rarely in patients after SCT. Two possible mechanisms include (1) an immune reconstitution syndrome, supported by stereotypical neuropathy types (radiculoplexus and polyradiculoneuropathies), monophasic course and temporal association with SCT and (2) a paraneoplastic phenomenon, supported by frequent early malignancy recurrence following IMN.

Lumbosacral Radiculoplexus Neuropathy After COVID-19.

INTRODUCTION: Lumbosacral Radiculoplexus Neuropathy (LRPN) is a subacute, painful, paralytic, asymmetric immune-mediated lower-limb neuropathy associated with weight loss and diabetes mellitus (called DLRPN). Approximately one-third of LRPN cases have a trigger. Our purpose is to show that COVID-19 can trigger LRPN. CASE REPORT: We describe the clinical, neurophysiological, radiologic, and pathologic findings of a 55-year-old man who developed DLRPN after severe acute respiratory syndrome coronavirus-2 infection. Shortly after mild coronavirus disease 2019 (COVID-19), the patient developed severe neuropathic pain (allodynia), postural orthostasis, fatigue, weight loss, and weakness of bilateral lower extremities requiring wheelchair assistance. One month after COVID-19, he was diagnosed with type 2 diabetes mellitus. Neurological examination showed bilateral severe proximal and distal lower extremity weakness, absent tendon reflexes, and pan-modality sensation loss. Electrophysiology demonstrated an asymmetric axonal lumbosacral and thoracic radiculoplexus neuropathies. Magnetic resonance imaging showed enlargement and T2 hyperintensity of the lumbosacral plexus. Cerebral spinal fluid (CSF) showed an elevated protein (138 mg/dL). Right sural nerve biopsy was diagnostic of nerve microvasculitis. He was diagnosed with DLRPN and treated with intravenous methylprednisolone 1 g weekly for 12 weeks. The patient had marked improvement in pain, weakness, and lightheadedness and at the 3-month follow-up was walking unassisted. CONCLUSION: COVID-19 can trigger postinfectious inflammatory neuropathies including LRPN.

Painless diabetic motor neuropathy: a variant of diabetic lumbosacral radiculoplexus Neuropathy?

OBJECTIVE: Occasionally, diabetic patients develop painless, lower-limb, motor predominant neuropathy. Whether this is a variant of diabetic lumbosacral radiculoplexus neuropathy (DLRPN) (a painful disorder from ischemic injury and microvasculitis), a variant of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) or another disorder is unsettled. Here, we characterize the clinical and pathological features of painless diabetic motor predominant neuropathy. METHODS: We identified patients with this syndrome who underwent nerve biopsy. We compared pathological features to 33 DLRPN and 25 CIDP biopsies. RESULTS: 23 patients were identified (22 had type 2 diabetes mellitus); 12 men; median age 62.2 years (range 36-78); median weight loss 30 pounds (range 0-100). Overall, the clinical features were similar to DLRPN except painless patients had more symmetrical and upper limb involvement, with slower progression and more severe impairment. Physiological testing demonstrated pan-modality sensory loss, autonomic abnormalities and axonal polyradiculoneuropathies. Nerve biopsies were similar to DLPRN showing ischemic injury (multifocal fiber loss [11/23], perineural thickening [18/23], injury neuroma [11/23], neovascularization [17/23]) and evidence of altered immunity and microvasculitis (epineurial perivascular inflammation [23/23], prior bleeding [11/23], vessel wall inflammation [15/23], and microvasculitis [3/23]). In contrast, CIDP biopsies did not show ischemic injury or microvasculitis but revealed demyelination and onion-bulbs. INTERPRETATION: 1) Painless diabetic motor neuropathy is painless DLRPN and not CIDP and is caused by ischemic injury and microvasculitis. 2) The clinical features of painless DLRPN are different from typical DLPRN being more insidious and symmetrical with slower evolution. 3) The slower evolution may explain the lack of pain.

Immune trigeminal sensory neuropathy with esophageal achalasia: improvement with long-term immunotherapy.

We report a patient who developed subacute facial-predominant numbness and anhidrosis, oral incoordination, and esophageal achalasia with resultant cachexia. Great auricular nerve biopsy showed extensive epineurial perivascular inflammatory infiltrates. Sensation, sweating, and swallowing improved with pulse intravenous methylprednisolone given over 5 years. We suggest that the patient's deficits, including achalasia, were due to an immune-mediated sensory and autonomic neuropathy and that, in such cases, pathologic studies of the great auricular nerve may be diagnostically informative.

Amphiphysin-IgG autoimmune neuropathy: A recognizable clinicopathologic syndrome.

OBJECTIVE: To define the clinicopathologic features of amphiphysin-immunoglobulin G (IgG)-mediated neuropathy. METHODS: Patients examined at our institution from January 1, 1995, to September 30, 2018, with amphiphysin-IgG by indirect immunofluorescence and Western blot, were reviewed. Their phenotypes were compared to cases of coexisting collapsin response-mediator protein-5 (CRMP5)-IgG or anti-neuronal nuclear antibody type 1 (ANNA1-IgG) and CRMP5-IgG autoimmunity. Improvement in modified Rankin Scale (mRS) (≥1) on follow-up was considered a favorable outcome. Amphiphysin RNA expression was assessed in healthy nerves. RESULTS: Fifty-three amphiphysin-IgG-positive cases were identified. Of 33 (60%) patients with neuropathy, 21 had amphiphysin-IgG alone, and 12 had coexisting autoantibodies (ANNA1-IgG, n = 8; CRMP5-IgG, n = 2; ANNA1-IgG and CRMP5-IgG, n = 2). The neuropathies in isolated amphiphysin-IgG autoimmunity included polyradiculoneuropathy (62%), diffuse sensory neuronopathy (35%), and facial neuropathy with gastroparesis (3%). Among these, pain (80%), breast cancer (63%), and CNS (57%) involvements commonly coexisted, and neuropathy frequently prompted breast cancer diagnosis (76%). Stiff-person spectrum disorder was the most common CNS accompaniment (45%). Nerve biopsies showed axonal loss (n = 6/6), subperineurial edema (n = 4/6), and CD4 predominant inflammation (n = 2/6). Median mRS score at last follow-up was 3.5; 58% of patients were immunotherapy-responsive. Patients with amphiphysin-IgG alone had more favorable immunotherapy response than patients with CRMP5-IgG polyneuropathy (n = 45) (44% vs 16%, p = 0.028, odds ratio 4.2, 95% confidence interval 1.1 to 15.5). Only 1/9 (11%) patients with amphiphysin-IgG with coexisting CRMP5-IgG or ANNA1-IgG had immunotherapy response. RNA amphiphysin expression occurred at low levels in nerve. CONCLUSION: Amphiphysin-IgG autoimmune neuropathy has a recognizable phenotype, is frequently immune responsive, and can prompt early diagnosis of breast cancer.

Recurrent Brachial Neuritis Attacks in Presentation of B-Cell Lymphoma.

We describe a 51-year-old woman who over 5 years had 9 painful monophasic attacks affecting the brachial plexus before a fascicular plexus biopsy diagnosed large B-cell lymphoma. The initial attacks were responsive to steroids with clinical resolution. At last attack, magnetic resonance imaging showed multifocal T2 hyperintensities and nodular gadolinium enhancement in the right brachial plexus not seen previously. Also seen were similar changes in the thoracic spinal cord, basal ganglia, cerebellum, and brainstem. Positron emission tomography revealed marked hypermetabolic activity of the plexus facilitating targeted fascicular brachial plexus biopsy, making the pathological diagnosis. Neurolymphomatosis affecting the peripheral nervous system typically presents with insidious painful progressive infiltration of nerves, roots, or plexi. Recurrent idiopathic brachial neuritis attacks (ie, Parsonage-Turner syndrome) in contrast most commonly are seen in persons with a family history and a discoverable genetic cause by SEPT9 mutations, which tested negative in this patient. This case illustrates how neurolymphomatosis, which represents a malignant transformation of B cells within peripheral nerves, can sometimes present with paraneoplastic immune-responsive neuritis mimicking Parsonage-Turner syndrome. Recurrence, an immune-refractory course or insidious progressive involvement of the nervous system, should raise suspicion of neurolymphomatosis.

Epidermal Nerve Fiber Quantification in Patients With Erythromelalgia.

IMPORTANCE: Erythromelalgia is a clinical diagnosis based on intermittent warmth, erythema, and pain in the distal extremities. One problem facing physicians is how to objectively test for this disease. Given that other painful conditions of the distal extremities (ie, neuropathy related to human immunodeficiency virus, diabetes, or Fabry disease) can be evaluated with a skin biopsy to visualize pathologically decreased densities of the small nerve fibers that innervate the epidermis, one hypothesis is that erythromelalgia could similarly be associated with a loss of epidermal nerve fiber density (ENFD). OBJECTIVES: To examine whether erythromelalgia is associated with a structural loss of small fibers using the ENFD technique and to compare this with functional studies of small nerve fibers. DESIGN, SETTING, AND PARTICIPANTS: In a retrospective study of 52 consecutive patients with erythromelalgia who were seen between September 1, 2010, and September 22, 2015, patients were interviewed and examined and their conditions clinically diagnosed by a board-certified dermatologist at a large tertiary referral center, where ENFD testing became a routine part of evaluating erythromelalgia in 2010. Thus, all 52 consecutive patients were included solely based on their clinical diagnosis of erythromelalgia. For quantification of ENFD, observers were masked to all patient information except for name and clinic number. MAIN OUTCOMES AND MEASURES: The hypothesis that patients with erythromelalgia would have decreased ENFD was formulated before data collection. Epidermal nerve fiber density, the primary outcome, is a measurement of the density of small nerve fibers within the epidermis. Secondary measures included functional small fiber evaluation, such as autonomic (heart rate, blood pressure, and sweat testing) and subjective testing of pain. RESULTS: In this cohort study, 52 consecutively seen patients were identified (female, 42 [80%]; median age, 44 years; age range, 13-82 years). Whereas only 5 of 52 patients (10%) had ENFD at or below the fifth percentile of healthy control individuals, most patients had functional abnormalities of these small fibers; 29 patients (60%) had abnormal sweat test results, 21 (42%) had abnormal pain thresholds, and 20 (38%) had abnormal blood pressure or heart rate control. CONCLUSIONS AND RELEVANCE: Unlike other diseases of the small nerve fibers that cause acral pain syndromes, erythromelalgia is not characterized by loss of ENFD. However, most patients have impaired function of these small fibers. Physicians would benefit from performing functional rather than structural small fiber studies when evaluating erythromelalgia.

Pediatric Nerve Biopsy Diagnostic and Treatment Utility in Tertiary Care Referral.

BACKGROUND: Pediatric neuropathies are both unique and similar to their adult counterparts, with genetic varieties thought to be more common. The objective of this work was to assess the utility of nerve biopsy in children at a tertiary referral center in light of availability of current genetic testing. METHODS: We retrospectively reviewed the clinical, nerve biopsy, and genetic testing findings of 316 pediatric (age ≤18 years) patients. RESULTS: Median age at diagnosis was 9.8 years (4 days to 18 years). Nerve biopsy was nontargeted in 198 (182 whole sural, seven superficial peroneal, and nine other), targeted in 21 (14 fascicular sciatic and seven brachial plexus), and unknown in 97 cases. Prebiopsy localizations and diagnoses were diverse, most commonly with length-dependent localizations (n = 150). Median follow-up was 6 months (0 to 480 months). A distinctive histopathologic diagnosis was made in 106 cases (33%), including inflammatory or immune (n = 30), neoplastic (n = 19), hereditary (n = 41), vasculitis (n = 10), and other (n = 6). Nerve biopsy confirmed the suspected diagnosis in 91 (29%) individuals and changed or refined the initial diagnosis in 182 (58%). Treatment modifications as a result of biopsy occurred in 80 (25%) cases; 59 (19% of the entire cohort) with clinical improvements noted, most commonly by immunotherapy (n = 30). Low diagnostic yield occurred in "hypotonic infants" without nerve conduction abnormalities. Pain at the biopsy site beyond 1 month was rare (n = 3; 1%). Forty-four patients underwent genetic testing. Among demyelinating varieties, mutations were identified in five of 11 (46%) cases compared with only six of 33 (18%) cases of axonal varieties. CONCLUSION: Pediatric nerve biopsy provides diagnostic information that frequently alters treatment recommendations. Furthermore, it leads to clinical improvements, especially in inflammatory immune neuropathies. For suspected inherited varieties, genetic testing has the highest diagnostic yield in demyelinating phenotypes.

Vasculitic neuropathy following exposure to minocycline.

OBJECTIVE: To report 3 patients with minocycline-induced autoimmunity resulting in peripheral nerve vasculitis. METHODS: We report 3 patients who, during minocycline treatment for acne vulgaris, developed subacute onset of pain and weakness caused by vasculitis in single and multiple mononeuropathy patterns. RESULTS: Each patient underwent either a nerve or muscle biopsy that confirmed vasculitis. One patient additionally developed systemic symptoms (including fever, fatigue, and night sweats) and another had a posterior circulation stroke. Symptoms developed with either early or prolonged use of minocycline. Despite withdrawal of minocycline, patients needed long-term immunotherapy to gain neurologic improvement. CONCLUSIONS: Our findings suggest that the typical neuropathy associated with minocycline use is painful single or multiple mononeuropathy due to peripheral nerve vasculitis, which may also be accompanied by presumed CNS vasculitis (presenting as stroke).

Chronic meralgia paresthetica and neurectomy: a clinical pathologic study.

OBJECTIVE: To understand the pathologic and clinical correlates of patients with chronic meralgia paresthetica (MP) undergoing lateral femoral cutaneous nerve (LFCN) neurectomy. METHODS: A retrospective cohort approach was utilized to identify 7 patients undergoing LFCN neurectomy for intractable pain. Control autopsied LFCN was obtained. Clinical, radiologic, and electrophysiologic features were reviewed. RESULTS: In identified cases, preoperative symptoms included severe lateral thigh pain and numbness. The duration of symptoms prior to surgery ranged from 2 to 15 years. Body mass index (BMI) varied from 20 kg/m(2) to 44.8 kg/m(2) (normal-morbidly obese), with 6 out of 7 patients being obese. No patients were diabetic. Focal nerve indentation at the inguinal ligament was seen intraoperatively and on gross pathology in 4 of 7 cases. Multifocal fiber loss, selective loss of large myelinated fibers, thinly myelinated profiles, regenerating nerve clusters, perineurial thickening, and subperineurial edema were seen. None of these features were observed in control nerve. Morphometric analysis confirmed loss of large myelinated fibers with small and intermediate size fiber predominance. Five patients had varying degrees of intraneural and epineurial inflammation. Six of 7 reported improved pain after neurectomy, sometimes dramatic. CONCLUSIONS: Patients with chronic MP and intractable pain have an LFCN mononeuropathy with loss of nerve fibers. Pathologic and clinical study supports a compressive pathogenesis as the primary mechanism. Abnormal nerve inflammation coexists and may play a role in pathogenesis. These selected patients typically benefited from neurectomy at a site of inguinal ligament compression. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that patients with chronic MP LFCN neurectomy experience improvement in MP-related pain.