1 Division of Neurosurgery, Department of Neurosciences, College of Medicine and Philippine General Hospital, University of the Philippines Manila, Manila, Philippines.
2 Department of Otorhinolaryngology, College of Medicine and Philippine General Hospital, University of the Philippines Manila, Manila, Philippines.
3 Department of Laboratories, College of Medicine and Philippine General Hospital, University of the Philippines Manila, Manila, Philippines.
4 Department of Otorhinolaryngology, College of Medicine and Philippine General Hospital, University of the Philippines Manila, Manila, Philippines; Philippine National Ear Institute, National Institutes of Health, University of the Philippines Manila, Manila, Philippines.
5 Division of Neurosurgery, Department of Neurosciences, College of Medicine and Philippine General Hospital, University of the Philippines Manila, Manila, Philippines. Electronic address: kathleen.khu@neurosurgery.ph.