Citations

ABSTRACTAimTo report a novel case of biopsy‐proven, mass spectrometry‐confirmed, wild‐type transthyretin amyloidosis (ATTRwt) in nerve.MethodsThe patient was identified and evaluated in the peripheral nerve clinic. Our nerve laboratory's pathology database and the literature were searched for prior evidence of pathologically confirmed cases of ATTRwt.ResultsA 94‐year‐old man with a history of lumbar spinal stenosis presented to the neurology clinic with subacute‐on‐chronic progressive, upper limb predominant weakness along with numbness and tingling paresthesia. Electromyography (EMG) revealed multiple mononeuropathies involving the right median nerve at the wrist, right ulnar nerve, and right distal radial nerve superimposed upon an axonal predominant peripheral neuropathy along with multilevel lumbosacral radiculopathies. Extensive serology for causes of neuropathy and multiple mononeuropathies returned unremarkable. A diagnostic right superficial radial nerve biopsy was performed and showed congophilic material within a small epineurial vessel wall in the nerve tissue. Amyloid typing by mass spectrometry was performed and revealed ATTRwt. TTR gene sequencing returned normal. The patient was diagnosed with ATTRwt neuropathy and started on diflunisal therapy for neuropathy treatment.ConclusionThis case confirms the presence of ATTRwt deposition directly in nerve tissue as the likely cause of the patient's large fiber and multiple mononeuropathies, expanding our current understanding of ATTRwt‐associated disease. Proving the direct association of ATTRwt and neuropathy may open up amyloid‐specific treatments for this disease.

BACKGROUND MRI-guided targeted fascicular biopsy has been a valuable technique for diagnosing idiopathic neuropathies. It has an 80% yield and a minor permanent morbidity rate of 5%. OBSERVATIONS A 48-year-old woman with a history of localized amyloidosis to the orbital muscle 2 years earlier presented with new neurological symptoms. Extensive evaluations including skin, muscle, and distal cutaneous nerve biopsies were negative, and empirical treatment trials did not improve her condition. An MRI-guided targeted biopsy of the right ulnar nerve in the distal arm was planned. During surgery, a medial triceps branch arising from the ulnar nerve was identified and was biopsied along with a neighboring fascicle of the ulnar nerve to the flexor carpi ulnaris. The pathology of the ulnar nerve fascicle but not the contiguous triceps branch showed amyloid (AL [kappa] subtype on mass spectroscopy). The patient was started on treatment. LESSONS The positive biopsy of the ulnar nerve fascicle allowed targeted treatment of the neural amyloidosis. While the negative biopsy of the triceps branch could be attributed to sampling error, it could also be due to the fact that this branch found within the ulnar nerve is thought to originate from the radial nerve. https://thejns.org/doi/10.3171/CASE25484

ABSTRACTBackground and AimsNerve conduction studies (NCS) are integral to diagnosing chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), but their role in predicting treatment outcomes remains underexplored. This study evaluates NCS changes at first follow‐up (first NCS changes) as predictors of treatment success in CIDP, focusing on their correlation with clinical outcomes over time.MethodsNewly diagnosed CIDP patients meeting the 2021 EAN/PNS criteria were retrospectively evaluated. Baseline and first follow‐up NCS parameters were compared with clinical outcomes, assessed by the Neuropathy Impairment Score (NIS) and Inflammatory Neuropathy Cause and Treatment (INCAT) disability score. All patients received first‐line immunotherapy (intravenous immunoglobulin, corticosteroids, or plasma exchange).ResultsOf 39 treated patients, 26 (66.7%) were responders based on improving NIS trends, while 13 (33.3%) were nonresponders. Responders showed significant improvements at the first follow‐up in fibular compound muscle action potential (CMAP) amplitude, ulnar CMAP amplitude, summated CMAP amplitudes, and fibular motor conduction velocity. Changes in fibular CMAP amplitude consistently correlated with NIS (R = −0.8 to −0.6, p ≤ 0.004) and INCAT disability score improvements (R = −0.6 to −0.3, p ≤ 0.032) across all follow‐up intervals up to 60 months. Ulnar and summated CMAP amplitude changes also correlated with clinical outcomes, though their associations were less sustained than those of fibular CMAP amplitude.InterpretationThe first change in fibular CMAP amplitude is a reliable biomarker for predicting CIDP treatment response, with ulnar and summated CMAP amplitudes as alternatives when the fibular response is absent. Our findings highlight the utility of first NCS changes in monitoring and predicting treatment outcomes in CIDP.