MRI Scan in Snoring and Sleep Apnea_Investigation
Dr.K.O.Paulose FRCS DLO, Consultant ENT Surgeon, Jubilee Hospital, Trivandrum, Kerala, India
MRI Imaging: Evaluation and Follow up of Snoring and Sleep Apnea Patients
Obstructive sleep apnea (OSA) is caused by a blockage of the airway, usually when the soft tissue in the rear of the throat collapses and closes during sleep. In central sleep apnea, the airway is not blocked but the brain fails to signal the muscles to breathe. Mixed apnea, as the name implies, is a combination of the two. With each apnea event, the brain briefly arouses people with sleep apnea in order for them to resume breathing, but consequently sleep is extremely fragmented and of poor quality.
The condition is common in males aged between 30-60 years. The clinical symptoms include history of snoring, daytime hypersomnia and nocturnal choking or gasping. Obesity and ingestion of alcohol are predisposing factors. In some patients the structural compromise is due to anatomical factors such as micrognathia, retrognathia, adenotonsillar hypertrophy and macroglossia.
Velopharynx is the most common site of pharyngeal obstruction in these patients. Two factors maintain the patency of the pharyngeal airway in healthy persons even while sleeping: anatomic factor and a functional factor (synchronisation of the activities of the muscles of upper respiratory tract and nerves).
Polysomnography is the investigation of choice for establishing the diagnosis of SAS and for determining its severity. Because CT scan has high spatial resolution and provides tomographic images, it is often used to diagnose pharyngeal obstruction. However CT provides only axial images and cannot image the entire pharyngeal airway in a single plane.
MRI Imaging is a non-invasive modality that allows examination of the entire pharynx in multiple planes and in a short time, with no radiation exposure as compared to CT. It provides good temporal and a high contrast resolution and can evaluate the pharynx on a real time basis.MRI imaging is the best non-invasive modality for evaluation and follow-up of patients with obstructive sleep apnea.