Characterizing Expiratory Respiratory Muscle Degeneration in Duchenne Muscular Dystrophy Using MRI,Chest

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Characterizing Expiratory Respiratory Muscle Degeneration in Duchenne Muscular Dystrophy Using MRI
Chest ( IF 9.5 ) Pub Date : 2021-09-15 , DOI: 10.1016/j.chest.2021.08.078
Alison M Barnard ₁ , Donovan J Lott ₁ , Abhinandan Batra ₁ , William T Triplett ₁ , Rebecca J Willcocks ₁ , Sean C Forbes ₁ , William D Rooney ₂ , Michael J Daniels ₃ , Barbara K Smith ₁ , Krista Vandenborne ₁ , Glenn A Walter ₄

Affiliation

Background

Expiratory muscle weakness and impaired airway clearance are early signs of respiratory dysfunction in Duchenne muscular dystrophy (DMD), a degenerative muscle disorder in which muscle cells are damaged and replaced by fibrofatty tissue. Little is known about expiratory muscle pathology and its relationship to cough and airway clearance capacity; however, the level of muscle replacement by fat can be estimated using MRI and expressed as a fat fraction (FF).

Research Question

How does abdominal expiratory muscle fatty infiltration change over time in DMD and relate to clinical expiratory function?

Study Design and Methods

Individuals with DMD underwent longitudinal MRI of the abdomen to determine FF in the internal oblique, external oblique, and rectus abdominis expiratory muscles. FF data were used to estimate a model of expiratory muscle degeneration by using nonlinear mixed effects and a cumulative distribution function. FVC, maximal inspiratory and expiratory pressures, and peak cough flow were collected as clinical correlates to MRI.

Results

Forty individuals with DMD (aged 6-18 years at baseline) participated in up to five visits over 36 months. Modeling estimated the internal oblique progresses most quickly and reached 50% replacement by fat at a mean patient age of 13.0 years (external oblique, 14.0 years; rectus abdominis, 16.2 years). Corticosteroid-untreated individuals (n = 4) reached 50% muscle replacement by fat 3 to 4 years prior to treated individuals. Individuals with mild clinical dystrophic phenotypes (n = 3) reached 50% muscle replacement by fat 4 to 5 years later than corticosteroid-treated individuals. Internal and external oblique FFs near 50% were associated with maximal expiratory pressures < 60 cm H₂O and peak cough flows < 270 L/min.

Interpretation

These data improve understanding of the early phase of respiratory compromise in DMD, which typically presents as airway clearance dysfunction prior to the onset of hypoventilation, and links expiratory muscle fatty infiltration to pulmonary function measures.

中文翻译：

使用 MRI 表征杜氏肌营养不良症的呼气呼吸肌退化

背景

呼气肌无力和气道清除受损是杜氏肌营养不良症 (DMD) 呼吸功能障碍的早期迹象，这是一种退化性肌肉疾病，其中肌肉细胞受损并被纤维脂肪组织取代。对呼气肌病理学及其与咳嗽和气道清除能力的关系知之甚少；但是，可以使用 MRI 估计脂肪替代肌肉的水平，并表示为脂肪分数 (FF)。

研究问题

DMD 中腹呼气肌脂肪浸润如何随时间变化并与临床呼气功能相关？

研究设计和方法

DMD 患者接受腹部纵向 MRI 检查以确定腹内斜肌、腹外斜肌和腹直肌呼气肌的 FF。FF 数据用于通过使用非线性混合效应和累积分布函数来估计呼气肌退化模型。收集 FVC、最大吸气和呼气压力以及咳嗽流量峰值作为与 MRI 的临床相关性。

结果

40 名 DMD 患者（基线年龄为 6-18 岁）在 36 个月内参加了多达 5 次访问。建模估计腹内斜肌进展最快，并在平均患者年龄 13.0 岁时达到 50% 的脂肪替代（腹外斜肌 14.0 岁；腹直肌 16.2 岁）。未接受皮质类固醇治疗的个体 (n = 4) 在接受治疗的个体之前 3 至 4 年达到 50% 的肌肉被脂肪替代。具有轻度临床营养不良表型 (n = 3) 的个体比接受皮质类固醇治疗的个体晚 4 至 5 年达到 50% 的肌肉被脂肪替代。_{接近 50% 的内部和外部倾斜 FFs 与最大呼气压力 < 60 cm H 2} O 和峰值咳嗽流量 < 270 L/min相关。