[Association of an arachnoid cyst with heterotopic neuroglial tissue in the internal auditory canal].

OBJECTIVES

We report a case of an association of an arachnoid cyst with heterotopic neuroglial tissue in the internal auditory canal.

MATERIAL AND METHODS

A 66-year-old woman consulted for cochleovestibular syndrome.

RESULTS

MRI demonstrated a lesion with spontaneous hypersignal on T1- and T2-weighted images, instigating surgical exploration. We discovered a hematic arachnoid cyst associated with heterotopic neuroglial tissue arising in the internal auditory canal.

CONCLUSION

An arachnoid cyst arising within the cerebellopontine angle or the internal auditory canal is a rare occurrence. Clinical manifestations are identical with those produced by a cochleovestibular schwannoma. MRI usually demonstrates a nonenhancing isointense cystic mass with cerebrospinal fluid on all sequences (hypointense on T1-weighted and hyperintense on T2-weighted images). These lesions are usually monitored. Spontaneous hypersignal on T1- and T2-weighted images makes diagnosis difficult, as in our case, leading to surgical exploration.