Evidence of small-fiber neuropathy (SFN) in two patients with unexplained genital sensory loss and sensory urinary cystopathy

Abstract

The term small-fiber neuropathy (SFN) refers to the type of polyneuropathies that preferentially damage the small unmyelinated and thinly myelinated sensory or autonomic neurons [1]. Skin biopsy to determine the epidermal nerve-fiber density (ENFD) is the most de- finitive method in the diagnosis of SFN, but autonomic function testing can also be useful [2]. Importantly, electromyography and surface nerve-conduction studies (EMG/NCS) do not capture the small scattered action potentials of small fibers, and thus are insensitive to small-fiber restricted neuropathies. Quantitative sensory testing is a subjective test that depends on patient volition, so it is not recommend- ed or reimbursed for clinical use [3]. Most generalized polyneuropathies first affect the distal parts of the limbs, such as the feet. They only rarely present proximally and the diagnosis of a non-length dependent SFN is usually associated with symptoms beginning in the hands, face, or torso. Onset in the pelvic region is rare and the diagnosis can be missed. We report on two patients with an unexplained syndrome of somatic and visceral uro-genital sensory deficit with histologic evidence of SFN.