Unusual case of posterior fossa syndrome and bilateral hypertrophic olivary degeneration after surgical removal of a large fourth ventricle ependymoma in an adult

Dear Editor, Posterior fossa syndrome (PFS) is a complication of posterior fossa tumor surgery in children and occurs in 11 %–29 % of patients. PFS includes a wide range of complex neurobehavioral and motor symptoms. Cerebellar mutism is the most characteristic and commonly found. Recovery is spontaneous, but most patients will have language dysfunction and longterm sequelae [3, 5]. This syndrome has only occasionally been documented in adults [7]. Hypertrophic olivary degeneration (HOD) is a rare neurological disease caused by lesions in the Guillain-Mollaret triangle. This triangle is formed by the red nucleus, the ipsilateral inferior olivary nucleus, and the contralateral dentate nucleus [1, 6, 9, 10, 12]. HOD affects both, children and adults. It occurs relatively frequently after posterior fossa surgery in children affected by midline primary malignant tumors [11]. HOD may be unilateral or bilateral and is not always associated with an identificable lesional cause [2]. Palatal myoclonus is the most common symptom of HOD, although it is not present in all cases [2, 4, 12]. These complications of posterior fossa surgery are well known separately, but seldom mentioned coexisting together and, to the best of our knowledge, never in an adult patient. We present an exceptional case of an adult patient who underwent surgery on a large fourth ventricle ependymoma and developed symptoms consistent with PFS, also presenting with bilateral HOD. We also demonstrate the common cause for these neurological disorders. A 48-year-old female with no previous medical history presented with a 3-month history of headache, vomiting, and gait imbalance. On neurological examination the patient only showed upward gaze palsy. Cranial MRI showed a large fourth ventricle tumor with gadolinium enhancement that enlarged the ventricle and produced severe obstructive hydrocephalus, brain stem compression, and tonsillar herniation (Fig. 1a). The patient underwent a ventriculoperitoneal shunt insertion followed by a tumor resection as a second stage procedure. This was performed through a midline transvermian approach with intraoperative neurophysiological monitoring for the cranial nerves and long tracts. Gross total removal of the tumor was achieved. No affectation of the neurophysiological potentials was noted during surgery. The patient recovered well, and she only complained about diplopia caused by a bilateral 6th cranial nerve paresis. The lower cranial nerves were preserved. On the 3rd postoperative day the patient presented with mutism, apathy, unconcern, slow voluntary movements, and hypotonia. An MRI showed total removal of the tumor and brain stem decompression, and ruled out any complications (Fig. 1b and c). Two weeks later, the patient began to speak—first only words, then progressively she was able to construct simple sentences. However, the speech flow was severely affected, and neurobehavioral problems such as apathy, unconcern, and lack of initiative remained, as well as slow voluntary movements, hypotonia, and dysmetria. The patient was sent to a rehabilitation center and showed motor function improvement. The dysmetria diminished, and she was able to walk with almost no support. The frontal-like symptoms and speech problems persisted. Histopathological analysis confirmed grade 2 ependymoma. Six months after surgery, the patient presented with dysphagia, dysarthria, intention tremor, and gait worsening. The neurobehavioral problems remained * Demian Manzano-Lopez Gonzalez 95324@parcdesalutmar.cat; dml8923@yahoo.es