To compare the electrodiagnostic studies of hATTR and wt-TTR amyloid neuropathy.

Amyloidosis are a group of diseases characterized by tissue deposition of insoluble proteins and fibril aggregates oriented in a β-pleated sheet structure that form unbranched amyloid fibrils. Amyloid neuropathy is a common manifestation of hATTR and wt-TTR amyloidosis. This can present as focal, multifocal or diffuse neuropathies involving sensory, motor and/or autonomic fibers.

Electrodiagnostic studies of 34 biopsy confirmed patients were reviewed, of which 18 were confirmed hATTR (FAP stages I-II) and 15 were wt-TTR (PND score stages I-III). Data on latency and amplitude of motor (median, ulnar, peroneal, tibial) and sensory (median, ulnar, sural, superficial peroneal) nerves were gathered. Pattern of active denervation was also noted. 

Sensorimotor polyaxonopathy was seen in 61.1% (11/18) in hATTR and 86.6% (13/15) in wt-TTR groups. Median neuropathy at wrist was found in 83.3% (15/18) and 93.3% (14/15) in hATTR and wt-TTR groups respectively. Ulnar neuropathy at elbow was found in 16.6% (3/18) of hATTR and absent in wt-TTR.

In hATTR 61.1% (11/18) and 33.3% (6/18) had prolonged peak latency in median palm and digit sensory responses respectively whereas in wt-TTR it was 53.3% (8/15) and 13.3% (2/15). Ulnar sensory responses with prolonged peak latency was seen in 33.3% (6/18) and 20% (3/15) in hATTR and wt-TTR respectively. Sural and superficial peroneal responses were absent in 88.8% (16/18) and 85.7% (12/14) respectively in hATTR while in wt-TTR it was 93.3% (14/15) and 92.3% (12/13).

Active denervation in either gastrocnemius was 50% (9/18) of hATTR and 53.3% (8/15) of wt-TTR groups.

Sensorimotor polyaxonopathy was higher in the wt-TTR compared to hATTR. There was also slight predominance of ulnar neuropathy at elbow in hATTR type. Median neuropathy, sensory responses in lower extremities and areas of active denervation were all comparable in both groups.