Hyo-Mental Angle and Distance: An Important Adjunct in Airway Assessment of Adult Mucopolysaccharidosis

Abstract

Background: Mucopolysaccharidosis (MPS) is a rare congenital lysosomal storage disorder with complex airways. High anterior larynx is assessed by thyromental distance (TMD) nasendoscopy. A simpler method to assess this hyoid bone is described. The distance between the central-hyoid and symphysis of the mandible (hyo-mental distance; HMD) and inclination of this line to the horizontal axis (hyo-mental angle; HMA) in neutrally positioned patients is investigated. Methods: HMA, HMD in MPS, and non-MPS were compared, and their correlation with height and weight were assessed. Results: 50 adult MPS patients (M = 32, F = 18, age range = 19–66 years; mean BMI = 26.8 kg/m2) of MPS I, II, III, IV, and VI were compared with 50 non-MPS (M = 25, F = 25; age range = 22–84 years; mean BMI = 26.5 kg/m2). Mean HMA in MPS was 25.72° (−10 to +50) versus 2.42° (−35 to +28) in non-MPS. Mean HMD was 46.5 (25.7–66) millimeters in MPS versus 41.8 (27–60.3) in non-MPS. HMA versus height and weight showed a moderate correlation (r = −0.4, p < 0.05) in MPS and no significant correlation (r < 0.4, p > 0.05) in non-MPS. HMD versus height and weight showed no correlation (r < 0.4, p > 0.05) in both groups. Conclusions: HMA seems more acute in MPS despite nearly the same HMD as non-MPS, signifying a high larynx, which may be missed by TMD.

Airway and Anaesthetic Management of Adult Patients with Mucopolysaccharidoses Undergoing Cardiac Surgery

“…Often these patients have a short neck, large head and spinal pathology [ 19 , 20 , 21 ], making any form of manipulation of the neck risky. These patients also have a high and anterior larynx [ 14 , 23 ], making visualisation of the laryngeal inlet extremely difficult.…”

“…Laryngeal height and position were assessed by nasendoscopy and on CT scan. Hyomental distance (HMD) and hyomental angle (HMA) [ 23 ] were used to assess the severity of laryngeal malposition. The subglottic diameter was calculated using the CT scan and indicated the maximum size of the endotracheal tube that could be used.…”

Non-cardiac Manifestations in Adult Patients With Mucopolysaccharidosis

“…Guided by mouth opening, modified mallampati grade ( 19 ), cervical spine mobility, high or anterior larynx assessed either by thyromental distance (TMD) ( 20 ), nasendoscopy or existing cross-sectional images. A novel method has also devised to assess high or anterior larynx by measuring the distance between hyoid bone and mentum, hyomental distance and its inclination to horizontal, hyomental angle ( 21 ).…”

“…Airway scoring can be performed using SMAS ( 30 ). The indicators of difficult oral intubation include poor mouth opening, reduced cervical spine mobility, prominent teeth, high mallampati grade, high and anterior larynx shown on nasendoscopy and by calculating hyo-mental distance, hyo-mental angle ( 21 ). Blind passage of bougies and multiple airway intubation attempts should be avoided.…”