“…We were unable to perform a histologic analysis of the lesion and diagnosis of thoracic arachnoid web, and its differentiation from neoplasm was based on neuroimaging findings. 47,48 The differentiation between obstructive hydrocephalus and normal pressure hydrocephalus was made on initial neuroimaging findings of focal heterogeneous CSF flow voids in the thoracic region suggestive of obstruction. Furthermore, improved (synchronous) CSF flow following the procedure was more suggestive of obstructive hydrocephalus (see Figure 4).…”