AI Summary
A man from rural China had weakness in his left upper limb. An MRI showed a cyst in his brain containing a parasite. Tests didn't find antibodies in his spinal fluid, but surgery confirmed the diagnosis. Cysts like this are rare.
A 54-year-old man from rural China presented with a 4-month history of proximally progressive weakness in the left upper limb, where diminished strength and hyperreflexia were noted. Head MRI showed a 5.5 x 4.8 x 4.6-cm right frontoparietal septate cyst with an enhancing mural nodule (Figure 1, A–C). CT revealed foci of calcification (Figure 1D). Diagnosis of neurocysticercosis was suspected, given the imaging findings suggesting a loculated cysticercus containing calcification and an enhancing scolex. Of interest, ELISA-based detection of cysticercus-specific antibodies in the CSF was unremarkable. CSF protein and cell count were also normal. During exploratory surgery, clear fluid with yellow nodules and daughter cysts was removed from the subarachnoid cyst, revealing foci of granulomatous inflammation on brain parenchyma (Figure 2). Pathologic examination identified Taenia solium larvae (eFigure 1, links.lww.com/WNL/C956). Giant subarachnoid cysticerci over the cerebral convexities are very rare.1 Absence of CSF antibodies in patients with radiographic findings suggestive of subarachnoid neurocysticercosis should not preclude its diagnosis.2