PMD are a rare phenomenon that has been described in patients with multiple sclerosis since the 1940s. PMD are typically responsive to carbamazepine. One subtype of PMD is paroxysmal dysarthria and ataxia syndrome (PDA), characterized by stereotyped episodes of dysarthria and ataxia, lasting seconds and recurring several times per day. This is thought to be due to transverse ephaptic transmission between demyelinated axons in the brainstem. Recently, cases of PDA in other neuroinflammatory diseases such as Behcet’s disease, MOG-antibody disease (MOGAD), Bickerstaff encephalitis, and anti-NMDA encephalitis have been described but the spectrum of PMD in neuroinflammatory diseases has not been sufficiently studied. 

We describe in detail five patients with CNS inflammatory diseases who developed PMD. Underlying diseases were chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS), MS, MOGAD, and post-infectious encephalitis (COVID and LaCrosse virus). Four patients developed PDA, while one presented with paroxysmal esophageal contractions. Paroxysms were brief (less than 10 seconds) and frequent (up to hundreds of times a day).  On MRI, four patients had lesions in the medial midbrain and one had a lesion in a cerebellar peduncle. In four cases paroxysms were treated successfully with carbamazepine. All patients had complete or near-complete remission of their PMD.

This series highlights that different neuroinflammatory disorders can cause PMD. This is the first report of PDA in CLIPPERS or post-COVID encephalitis, and the second report in MOGAD. Most patients had lesions in the dorsal midbrain below the red nucleus, a site commonly reported to cause PDA. Treatment with carbamazepine was successful. PMD in neuroinflammatory disease is important to recognize as symptoms can be debilitating but successfully treated. This case series can help improve awareness of this rare condition.