Describe a case of Chronic Immune Sensory Polyradiculopathy (CISP) with optic neuropathy.

Chronic Immune Sensory Polyradiculopathy is a rare and treatable inflammatory condition that affects large, myelinated fibers of the posterior roots, sparing distal nerves. It is considered an isolated sensory variant of CIDP. Patients usually present with ataxia, sensory loss, without any objective weakness. Optic neuropathy has not been shown in CISP prior, but is reported with CIDP and Anti-NF-155 nodopathy.

A 37-year-old woman presented with paresthesia of the feet and hands, frequent falls, and vision changes over weeks to months without preceding illness. Her exam was notable for wide-based gait, decreased patellar reflexes, decreased pinprick below T10, and decreased vibratory sensation bilaterally to the knees. Ophthalmologic evaluation showed bilateral optic disc pallor. A lab workup, including vitamin deficiencies, infectious, rheumatologic, genetic, paraneoplastic, ganglioside panels was completed and was unremarkable apart from a folate of 2.6ng/mL. MRI of the brain and spine was notable for diffuse thickening of the cauda equina nerve roots with T2 prolongation and enhancement of the dorsal roots. Lumbar puncture was significant for elevated protein  of 118mg/dL. Nerve conduction studies were normal.  Somatosensory evoked potentials showed intact upper extremity sensory pathways but a conduction delay of peripheral origin in the lower extremities. Specifically, there was absent lumbar spine potentials and prolonged latency of the right posterior tibial nerve. This was concerning for CISP as the underlying cause. She received 2g/kg IVIG and IV Solumedrol.  She will undergo maintenance IVIG with hopes to further improve her symptoms.

This case highlights a rare case of CISP with prototypical features, MRI and SSEP findings with additional optic neuropathy, which could possibly highlight potential overlap with other CIDP variants or nodopathies. This case reinforces that, while rare, CISP should remain on the differential in the right clinical context.