Total 1354 patients performed MVD. A variety of offending vessels were found in all of the 1354 patients. The offending vessels were the anterior-inferior cerebellar artery (AICA) in 670 (53.5%) patients, the posterior-inferior cerebellar artery in 382 (30.4%) patients, the vertebral artery in 21 (1.6%) patients, venous structure in 1 (0.1%) patients, two or more vessels in 180 (14.5%) patients. The right side was affected in 671 patients and the left in 683 patients ().
Characteristics and operative findings of 1354 patients
Cranial nerve palsy included immediate facial weakness in 43 (3.2%), immediate hearing loss in 39 (2.89%), delayed facial weakness in 100 (7.4%), one delayed hearing loss (0.1%), one delayed sixth nerve palsy (0.1%). There was no sixth nerve palsy immediately. Among delayed facial palsy patients, there were 33 men and 67 women who ranged in age from 25 to 65 years (mean age : 47.8 years) and the mean duration of symptoms was 5.8 years (range : 3 months-28 years). The onset of palsy occurred in postoperative 11.2 days in average (range : 2-23 days) (, ). The weakness was assessed by the House-Brackmann (HB) scale, and 30 patients were HB Grade II, 54 patients were grade III and patients were grade IV.
Factors that affect delayed facial palsy
The onset time for delayed facial palsy averaged 11.2 days with a range between 2 to 23 days. DFP : delayed facial palsy.
Recently, combined therapy was accepted most generally for DFP, 94 patients were given acyclovir (30 mg/kg/day) and prednisolone (1 mg/kg/day) for at least two weeks21)
. Eighty-six patients (86%) improved to complete recovery (Grade I) and eight patients improved to minimal weakness (Grade II). The time to recovery averaged 64.1 days (range : 16-270 days) ().
The time to recovery averaged 64.1 days (range : 16-270 days). DFP : delayed facial palsy.
We reviewed one unusual case of delayed hearing loss. A 71-year-old female underwent MVD for HFS. Magnetic resonance imaging showed that the right AICA was in close proximity to the REZ of the ipsilateral facial nerve. The operation was uneventful and BAEP were monitored at a baseline level throughout preparation. Delayed latency and amplitude of Peak V decline occurred during retraction of the cerebellum. Releasing the retractor improved the BAEP, and the BAEP recovered to baseline. After MVD, the patient had no subjective hearing impairment. Three weeks after the MVD, ipsilateral hearing loss occurred.
PTA-SA was performed and showed scale-out on the operated side (). Steroid medication in the form of methylprednisolone 40 mg/mL was given intratympanicly at a dose of 0.5 mL/day over 3 weeks3,22)
. One month after onset, ipsilateral hearing function improved and the PTA-SA showed a 78 dB deficit on the operated side (). Hearing loss improved a little, but was not cured to the point of achieving serviceable hearing.
Three weeks after MVD, PTA-SA shows scale-out on the operated side. MVD : microvascular decompression, PTA-SA : pure tone audiometry and speech discrimination.
One month after onset, PTA-SA shows ipsilateral hearing function improved. PTA-SA : pure tone audiometry and speech discrimination.
We experienced a rare case of isolated sixth nerve palsy. A 50-year-old woman underwent MVD for right-sided HFS. The procedure was uneventful. Three weeks after MVD, she developed delayed isolated ipsilateral sixth nerve palsy causing temporary lateral rectus weakness and diplopia. After 8 weeks, the palsy fully resolved spontaneously without any medical or surgical treatments11)