Shyam Sundar Krishnan1, Pulak Nigam2, Poonam Mohanty2, Madabhushi Chakravarthy Vasudevan2, Mohan Kameswaran3. 1. Dr. Achantha Lakshmipathi Neurosurgical Centre, Post Graduate Institute of Neurological Surgery, Voluntary Health Services Multi-Speciality Hospital & Research Centre, TTTI Post, Taramani, Adyar, Chennai, Tamil Nadu, 600113, India. shyamsundarkrishnan76@gmail.com. 2. Dr. Achantha Lakshmipathi Neurosurgical Centre, Post Graduate Institute of Neurological Surgery, Voluntary Health Services Multi-Speciality Hospital & Research Centre, TTTI Post, Taramani, Adyar, Chennai, Tamil Nadu, 600113, India. 3. Madras ENT Research Foundation, No. 1, 2nd Cross Street, RA Puram, Chennai, Tamil Nadu, 600028, India.
Abstract
INTRODUCTION: Auditory brainstem implant (ABI), a standard technique in treatment of profound sensorineural hearing loss in patients with neurofibromatosis 2, is now being increasingly employed in children with congenital bilateral sensorineural hearing loss, as in Michele's deformity. A detailed knowledge of the relevant surgical anatomy of the lateral recess and its anatomical landmarks including the flocculus, the choroid plexus and the root entry zones of facial-vestibulocochlear and glossopharyngeal-vagus nerve complexes and their anatomical variants is mandatory, as it is the conduit for electrode array placement. The placement of electrode may be eased or impeded by these variations. MATERIALS AND METHODS: Thirty-two children with congenital bilateral hearing loss underwent surgery through retromastoid suboccipital approach for placement of auditory brainstem implant. The preoperative anatomy was reviewed in detail during procedure and again later in the operative videos. RESULTS: The flocculus was classified into four grades based on its anatomy and relations. Among these, grade II (11 children) was the commonest while grade IV (five children) was least common. Choroid plexus was variable in size across grades of flocculus. Difficulty in defining the anatomy was significantly more (p value = 0.003) in the group with higher grade flocculus (grade III and IV) than in lower grade flocculus (grade I and II). CONCLUSION: The flocculus in these patients is classifiable into one of the four grades and the surgical nuances such as difficulty in defining the anatomy for placement of ABI are dependent on the characteristics exhibited by the floccular anatomy and relations.
INTRODUCTION: Auditory brainstem implant (ABI), a standard technique in treatment of profound sensorineural hearing loss in patients with neurofibromatosis 2, is now being increasingly employed in children with congenital bilateral sensorineural hearing loss, as in Michele's deformity. A detailed knowledge of the relevant surgical anatomy of the lateral recess and its anatomical landmarks including the flocculus, the choroid plexus and the root entry zones of facial-vestibulocochlear and glossopharyngeal-vagus nerve complexes and their anatomical variants is mandatory, as it is the conduit for electrode array placement. The placement of electrode may be eased or impeded by these variations. MATERIALS AND METHODS: Thirty-two children with congenital bilateral hearing loss underwent surgery through retromastoid suboccipital approach for placement of auditory brainstem implant. The preoperative anatomy was reviewed in detail during procedure and again later in the operative videos. RESULTS: The flocculus was classified into four grades based on its anatomy and relations. Among these, grade II (11 children) was the commonest while grade IV (five children) was least common. Choroid plexus was variable in size across grades of flocculus. Difficulty in defining the anatomy was significantly more (p value = 0.003) in the group with higher grade flocculus (grade III and IV) than in lower grade flocculus (grade I and II). CONCLUSION: The flocculus in these patients is classifiable into one of the four grades and the surgical nuances such as difficulty in defining the anatomy for placement of ABI are dependent on the characteristics exhibited by the floccular anatomy and relations.
Authors: Marc S Schwartz; Steven R Otto; Robert V Shannon; William E Hitselberger; Derald E Brackmann Journal: Neurotherapeutics Date: 2008-01 Impact factor: 7.620