Myotonic dystrophy type 1 with normal pressure hydrocephalus-like neuroimaging and a negative tap test: diagnostic pitfalls and management considerations

Myotonic dystrophy type 1 (DM1) is a multisystem, autosomal dominant disorder that often manifests with distal muscle weakness, myotonia, cataracts, cardiac conduction abnormalities, endocrine abnormalities, and characteristic craniofacial features.In older adults, imaging can reveal cerebral ventriculomegaly and, in a subset, a disproportionately enlarged subarachnoid space hydrocephalus (DESH) pattern that resembles normal pressure hydrocephalus (NPH)(1).This scenario complicates the management decision as the tap test and post-shunt response are inconclusive in these patients.We report a patient who was referred to us for normal pressure hydrocephalus, but detailed clinical evaluation of the patient and the family members led to the correct underlying diagnosis of DM1.