Infratentorial Hypoperfusion in Multiple Sclerosis

Long‐term disability in patients with multiple sclerosis (MS) results from axonal degeneration in the central nervous system, which might follow hypoperfusion in neurodegenerative diseases. This study aimed to clarify the distribution and clinical significance of brain hypoperfusion in patients with MS. We measured brain hypoperfusion in eight patients with relapsing–remitting MS using N‐isopropyl‐p‐iodine‐123‐iodoamphetamine single‐photon emission computed tomography with three‐dimensional stereotactic surface projection and stereotactic extraction estimation; moreover, we examined its clinical relevance. We detected marked hypoperfusion in the brainstem and cerebellum relative to that in the cerebrum. Each infratentorial segment, the midbrain, pons, and cerebellar anterior and posterior lobes, showed more severe hypoperfusion than the frontal and parietal lobes (n = 8). This was attributed mainly to oligoclonal band (OCB)‐negative patients (n = 3), even when OCB‐positive patients (n = 5) showed a similar trend. Consistently, OCB‐negative patients had lower blood flow at the pons, and cerebellar anterior and posterior lobes than OCB‐positive patients; however, both groups showed comparable hypoperfusion in the cerebral lobes. Hypoperfusion at the posterior cerebellar lobe and pons was correlated with poor performance in the Trail Making Test Part B (n = 6), indicating cognitive cerebellar dysfunction and cerebrocerebellar conductive disturbances. Patients with relapsing–remitting MS had lower infratentorial perfusion, which strongly links to OCB‐negativity. The distribution of brain hypoperfusion detected by N‐isopropyl‐p‐iodine‐123‐iodoamphetamine single‐photon emission computed tomography indicated pathological heterogeneity in relapsing–remitting MS. The infratentorial hypoperfusion is possibly associated with neurodegeneration.