Unveiling polyneuropathy: Imaging insights from a unique case

A 58-year-old woman presented with one month of symmetrical motor weakness and sensory disturbances affecting all limbs, predominantly lower limbs, accompanied by vertigo and reduced hearing. No autonomous symptoms or history of infection, immunodeficiency, or malignancy. Prior episodes in 1994, 2007, and 2021 with exacerbations and improvement. No similar familial or childhood history.

MRI spine reveals mild lumbar scoliosis with convexity to the left, and diffuse thickening of the cauda equina nerve roots, bilateral lumbosacral exiting nerve roots, cervical cord (from C4 to C7 levels), and bilateral brachial plexus nerve roots, exhibiting T1 isointense, T2 iso to mildly hyperintense, and STIR hyperintense signals with mild enhancement (Figures 1a, 1b, 1c, 2a, 2b, 3a, 3b, 3c, 4a and 4b). The thickened cauda equina nearly fills the spinal canal, with minimal surrounding cerebrospinal fluid (CSF). The thickened exiting nerve roots occupy the entire neural foramen, obliterating the perineural fat. Bilateral intercostal nerves also show diffuse thickening. Few perineural cysts are also noted.

USG shows diffusely thickened and hypoechoic appearance of the bilateral peripheral nerves, including the median, ulnar, tibial and common fibular nerves (Figures 5a and 5b).

Background

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired immune-mediated disorder where progressive or relapsing-remitting symptoms persist for months to years [1]. It primarily involves demyelination of proximal peripheral nerves, notably affecting nerve roots as evidenced in autopsy studies [2]. CIDP is commonly referred to as the chronic counterpart of acute inflammatory demyelinating polyradiculoneuropathy, which is the demyelinating form of Guillain–Barré syndrome. The affected nerves exhibit segmental infiltration with inflammatory cells (lymphocytes) and demyelination. Over time, Schwann cells proliferate, and collagen is deposited, leading to nerve thickening and the distinctive onion bulb appearance [3].

Clinical Perspective

Patients typically experience gradual, prolonged weakness affecting both proximal and distal muscles, along with reduced reflexes and sensory alterations. Symptoms usually persist longer than 2 months, with periods of relapse and remission over years, significantly impacting quality of life. Cranial nerve involvement occurs in only 11% of the cases and primarily manifests as facial and bulbar nerve palsies when severe [4].

Clinical assessment, nerve conduction studies (NCS), and positive nerve biopsy collectively confirm the diagnosis and differentiate it from other polyneuropathies [5]. CSF analysis reveals characteristic albuminocytologic dissociation. Approximately 85% to 90% of CIDP patients exhibit elevated protein levels and mild pleocytosis, typically fewer than 10 cells/mm³ [6]. While not definitive, radiological findings can enhance clinical sensitivity for this disease.

Imaging Perspective

MRI findings of nerve root hypertrophy, increased signal intensity, or abnormal enhancement in cervical/lumbar regions, brachial/lumbar plexus, or cauda equina are recognised as supportive criteria for diagnosing patients who meet the electrodiagnostic criteria for possible CIDP, as per the second revision (2021) of the European Academy of Neurology (EAN)/PNS guidelines on CIDP diagnosis and treatment [7]. Involvement of intercostal nerves and cranial nerve involvement have also been described.

Ultrasound studies report large hypoechoic nerves, with diffusely increased cross-sectional area [8].

Outcome

Diagnosing CIDP is crucial because effective treatments like steroids, intravenous immunoglobulin, plasmapheresis, and immunosuppression are available [3]. NCS, in this case, revealed motor and sensory involvement evidenced as slowed nerve conduction velocities, prolonged distal latencies and conduction block, and CSF analysis showed albuminocytologic dissociation. Treatment was initiated with steroids, which resulted in a noticeable improvement in symptoms.

Take Home Message / Teaching Points

CIDP is a rare, yet treatable condition, highlighting the critical need for diagnosis. A comprehensive imaging evaluation of multiple regions, including the brachial and lumbosacral plexuses, intercostal nerves, cauda equina and cranial nerves, assist in identifying distinctive patterns that contribute to an accurate diagnosis, thereby guiding targeted therapy.

Written informed patient consent for publication has been obtained.