BACKGROUND- Sensory neuronopathies are caused by impairment in the function or disturbance in the structure of the unipolar sensory neurons that reside in the spinal dorsal root and trigeminal ganglia. Their vulnerability to pathogenic factors, such as immune effectors, toxins, and infections, may stem from lack of an effective blood-nerve barrier in the dorsal root ganglia.
REVIEW SUMMARY- Patients typically present with profound, often asymmetric proprioceptive and vibratory sensory loss with ataxia and variable degrees of pain. Muscle stretch reflexes are absent. Strength is remarkably preserved. The mode of onset may be acute, subacute, or chronic. Supportive electrophysiological features are reduced or absent sensory potentials in the setting of essentially normal motor responses. Recognized causes comprise a paraneoplastic disorder (anti-Hu antibody positive); Sjögren's syndrome; an idiopathic form (probably immune-mediated in most patients); and toxic, nutritional, and infectious disorders. Sural nerve biopsies in patients with sensory neuronopathy show loss of large myelinated fibers. The clinical course is variable, ranging between relentless progression and stabilization with functional recovery. Treatments for the paraneoplastic and immune-mediated disorders comprise corticosteroids, plasma exchange, and various immunosuppressive agents, but they have generally not met with success.
CONCLUSION- Sensory neuronopathies are an important group of disorders that may be early warning signals of a systemic illness or disease process such as an occult neoplasm, autoimmune disease, nutritional deficiency, or unrecognized toxic exposure. The differential diagnosis extends across a broad spectrum of conditions that target the distal and peripheral processes of the dorsal root ganglion neuron. Although most sensory neuronopathies have responded poorly to treatment, prompt recognition is important because treatment begun in the earliest stages might stem the further loss of sensory neurons.