The effects of radiation therapy (RT) on cranial and peripheral nerves have been described as RINP.

Focal sites as the brachial and sacral plexus as well as cranial and individual nerves (e.g. sciatic, phrenic) can be affected. Rarely, prior RT can also induce malignant peripheral nerve sheath tumors. Due to RT of the sacral plexus an asymmetric neuropathy-like syndrome develops after a latency of years. Usually, patients present with a mostly sensory, asymmetric and progressive neuropathy without pain.

Case 1: A 56-year old female had a history of a colon cancer with surgery, followed by RT. 5 years later she presented with stocking-like sensory symptoms in the feet. NCV studies showed an absence of the sural nerves bilaterally, motor function was normal. In EMG complex repetitive discharges were noted.

Case 2: A prostate cancer was resected in a 65-year old male. After a year he received 75 Gy of local RT. Within five years he presented with mild, asymmetric, distal sensory symptoms in the feet, which progressed to unilateral foot drop. In EMG pseudomyotonic discharges were found.

The suspicion of RIPN arises with history of prior focal RT, resulting in a progressive painless asymmetric neuropathy with insidious progression. NCV studies show usually axonal changes and EMG demonstrates continuous discharges, typical for RT injury.

As the number of long term survivors is increasing, RINP will be observed more frequently in the future and must be distinguished from local recurrence and other causes of neuropathy.

Pathogenetically, a post RT damage of vessels and fibrosis is assumed. There is increasing awareness, that not only the nerves but also their surrounding supporting structures are involved resulting in the so called “radiation-fibrosis syndrome”.