| Macroglossia | Large tongue; usually a congenital disorder (present at birth) |
| MANDIBULAR ADVANCEMENT DEVICE (MAD) | Intra-oral device worn at night to hold the mouth closed and the lower jaw forward. Increases the space behind the tongue which lessens snoring and may help obstructive sleep apnoea. Obtained from dentists. |
| Mandibular Maxillary Osteotomy and Advancement (MMOA) | Procedure developed for patients with retrolingual obstruction patients with retropalatal and retrolingual obstruction who have not responded to CPAP and uvulopalatopharyngoplasty (UPPP). |
| MANOMETER (man-om-eater) | Device to measure the pressure being delivered by a CPAP machine (usually measured in centimetres of water {cmH20} - where a common CPAP pressure is about 10). |
| MAO | Monoamine Oxidase (an enzyme in the brain tissue) |
| MAOI | Monoamine Oxidase inhibitor (a class of anti-depressant.MHC) |
| Mask | The bit going over the nose. |
| Maxillofacial | Pertaining to the jaws and face. |
| Melatonin | Hormone secreted by the brains pineal gland. |
| MHC | Major Histocompatibility Complex |
| MICRO AROUSALS | Very brief "awakenings" perhaps only seen when the brain waves (EEG) are being monitored. |
| Micro-arousal | Partial awakening from sleep. |
| Micro-sleep | Period lasting up to a few seconds during which the polysomnogram suddenly shifts from waking characteristics to sleep. |
| Mirage Mask | A particular make of nasal mask. |
| MIRS | mandibular inclined repositioning splint |
| Mixed (sleep) apnea | Interruption in breathing during sleep beginning as a central apnea then becoming an obstructive apnea. |
| MMOA (MMA) | Mandibular Maxillary Osteotomy and Advancement |
| Monocyclic | A single major sleep period and a single major wake period in a 24-hour day. |
| Motor Activity in Sleep | Any muscular movement during sleep |
| Motor Atonia | The absence of muscle activity during sleep. |
| Movement arousal | Body movement associated with arousal or awakening; a sleep scoring variable. |
| MOVEMENT AROUSAL | These are short awakenings with minor body movements of which the sleeper is unaware. |
| Movement time | Term used in sleep record scoring to denote when EEG and EOG tracings are obscured for more than 15 seconds due to movement. |
| MRI | Magnetic Resonance Imagry |
| MSLT | Multiple Sleep Latency Test |
| MSLT | Multiple Sleep Latency Test. A nap study that measures how quickly you fall asleep during the day. It is used primarily to detect narcolepsy. |
| MUFFLES | Wax ear plugs. Less comfortable than the foam ones but more effective. From most chemists. |
| Multiple sleep latency test (MSLT) | A series nap tests utilized in the assessment of excessive daytime sleepiness. |
| Muscle Tone | Amount of tension in a muscle. |
| MWT | Maintenance of wakefulness test |
| MWT | Maintenance of Wakefulness Test. Measures how well you are able to stay awake during the day. It is used to evaluate how well treatment improves the daytime symptoms of a sleep disorder. |
| Myoclonus | Muscle contractions in the form of "jerks" or twitches. |
