Dystrophic muscle distribution in late-stage muscular dystrophy

Authors’ contributions: Celeste Michelle Pilato - Data collection and analysis, statistical analysis, text writing and editing. Melissa Sue Walker - Data collection, text writing, generating figures. Andrea M. Nguyen - Data collection, text writing and editing. McKay Elizabeth Hanna - Data collection, text writing. Scott Lanxing Huang - Data collection, text writing. Erika Morgan Lutins - Data collection. M. Alex Meredith - Course director, Data collection, analysis and archiving, statistical analysis, contributed to writing/editing the text and generating figures. Peter Jacob Haar - Radiologic advice, generated radiologic figure and legend. Mathula Thangarajh - Neurology advice, edited/reviewed text/figures. Hope Theresa Richard - Pathology advice, edited/reviewed text/figures. Woon Nam Chow - Pathology advice, Data collection, performed Pathology assays and photomicroscopy, edited/reviewed text/figures.

Conflict of interest: None.

Correspondence M. Alex Meredith Virginia Commonwealth University, School of Medicine, Department of Anatomy and Neurobiology 1101 E. Marshall St., Sanger Hall Rm 12-067, 23298-0709, Richmond, VA, USA Phone: +1 804 828-9533 marvin.meredith@vcuhealth.org

Figures (3)
Tables (1)

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Figure 1
Gross and histological appearance of selected muscles from case study of a 72-year-old white male with late-stage, adult onset muscular dystrophy. A representative gross image and its fat replacement score are shown (top-right) for a muscle with total fat replacement (score=3): the Tensor fascia lata; for a muscle with partial fat replacement (middle; score=2): the Soleus; and for a muscle with no apparent fat replacement (top left; score=1): the Flexor hallucis brevis. Examples of each of these levels of fat replacement are also illustrated at the histological level (bottom row) where photomicrographs of sections through the Pectoralis major muscle (right), Soleus (middle), and Flexor hallucis brevis (left) are shown. Stain: Hematoxylin and Eosin.

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Figure 2
Summary of dystrophic muscle distribution in a case of a 72-year-old white male with late-stage, adult-onset muscular dystrophy. The human musculature is depicted from anterior (left) and posterior (right) views showing both superficial and deep muscle planes. Colors indicate level of fat infiltration as grossly observed during dissection where yellow = complete fat replacement (score=3); orange = mixture of fat and muscle fascicles (score=2); brown = no apparent fat infiltrate in the muscle (score=1). Each muscle was identified and given a score and tabulated by region. These values are graphed where, in part (A) the average (± standard deviation) scores for appendicular muscles were significantly (“*”; p<0.001, ANOVA) higher among limb girdle muscles (pelvis, shoulder) than in the other regions, while those for axial muscles, shown in part (B) appeared to be uniformly unaffected.

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Figure 3
CT images from a case study of a 72-year-old white male with late-stage, adult onset muscular dystrophy. Part (A) is a frontal topogram of the entire cadaver showing diffuse fatty infiltration of skeletal muscles. Arrows indicate levels from which axial sections (B-E) are taken. In (B), the axial CT image is from mid-chest level, showing marked fat replacement of the pectoral muscles (arrows), and partial sparing of the serratus anterior and paraspinal muscles (arrowheads). Soft tissue gas in the upper arms and posterolateral back are related to the embalming process. In (C), at the level of the mid-pelvis, there is striking fatty replacement of the gluteal muscles (arrows), and partial sparing of the musculature of the abdominal wall (arrowheads). In the axial image in (D) at mid-thigh level, there is significant fatty replacement of the musculature of the anterior, posterior, and medial compartments of the thigh. The axial CT image in (E) is at the level of the mid-calf, which shows fatty replacement of the musculature of the leg, with substantial replacement and pseudohypertrophy of the posterior compartment musculature (arrows), and partial sparing of the anterior compartment musculature (arrowheads).

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Table 1
This tabulates the grossly observed fat-replacement scores for each muscle exposed in a case study of a 72-year-old white male cadaver with adult-onset, late-stage muscular dystrophy. Scores (as defined in the text) represent no apparent fat infiltration into the muscle (1), a mixture of fat and muscle fascicles (2), or total fat replacement (3). For comparison, also listed are percentage fat replacement values (“NI” = Not Infiltrated; “*” measured as a muscle group) for selected muscles calculated from MRI scans from.⁵5 Diaz-Manera J, Fernandez-Torron R, LLauger J, et al. Muscle MRI in patients with dysferlinopathy: pattern recognition and implications for clinical trials. J Neurol Neurosurg Psychiatry. 2018;89(10):1071-81. http://dx.doi.org/10.1136/jnnp-2017-317488. PMid:29735511.
http://dx.doi.org/10.1136/jnnp-2017-3174...

UPPER EXTREMITY	Score	MRI (%)	LOWER EXTREMITY	Score	MRI (%)	AXIAL	Score	MRI (%)
SHOULDER GIRDLE			PELVIC GIRDLE			TORSO/TRUNK
Trapezius	1		Psoas major/minor	2		Iliocostalis	2	93
Latissimus dorsi	2	75	Iliacus	3		Longissimus	2	86
Rhomboid major/minor	2	70	Quadratus lumborum	2		Spinalis	1
Levator scapulae	2		Tensor fascia latae	3	95	Transversospinals	1	89
Deltoid	2		Gluteus maximus	3		Serratus posterior sup/inf.	1
Teres major	2		Gluteus medius	3		External intercostal	1
Teres minor	2		Gluteus minimus	2	91	Internal intercostal	1
Supraspinatus	2	73	Piriformis	3		Innermost intercostal	1
Infraspinatus	2	74	Obturator ext/int.	3	86	Transversus thoracis	1
Subscapularis	2	81	Gemellus sup/inf.	3		Subcostalis	1
Pectoralis major	3		Quadratus femoris	3		Levator costarum	1
Pectoralis minor	3					Diaphragm	1
PROXIMAL (ARM)						Rectus abdominis	1
Triceps brachii long/lat/dp.	2	57	PROXIMAL (THIGH)			External abdominal oblique	2
Coracobrachialis	2		Sartorius	2		Internal abdominal oblique	2
Biceps brachii long/short	2	57	Rectus femoris	2		Transversus abdominis	1
Brachialis	2		Vastus lateralis	2		Cremaster	1
			Vastus intermedius	2		NECK
			Vastus medialis	3		Longus capitis	1
			Biceps femoris long/short	2	94	Scalene ant/mid/post.	1
			Semitendinosus	2	90	Sternocleidomastoid	1	NI
			Semimembranosus	2	95	Splenius	1	25*
			Gracilis	2		Semispinalis capitis	1	25*
			Pectineus	2		Platysma	1
			Adductor brevis	2		Cricothyroid	1
			Adductor longus	2	94	Arytenoidius	1
			Adductor magnus	2	94	Thyroarytenoid	1
DISTAL (FOREARM)			DISTAL (LEG)			Cricoarytenoid post/lat.	1
Extensor digitorum	1		Tibialis anterior	2		Digastric	1
Extensor digiti minimi	1		Extensor hallucis longus	1		Stylohyoid	1
Extensor carpi ulnaris	1		Extensor digitorum longus	1		Mylohyoid	1
Extensor carpi radialis long.	2		Gastrocnemius	2	99	Geniohyoid	1
Extensor carpi radialis brev.	2		Soleus	2	99	Sternohyoid	1
Brachioradialis	2		Popliteus	1		Sternothyroid	1
Supinator	2		Flexor hallucis longus	1		Thyrohyoid	1
Extensor indicis	1		Flexor digitorum longus	1		Omohyoid	1
Extensor pollicis long/brev.	1		Tibialis posterior	1		Longus colli	1
Abductor pollicis longus	1		Fibularis longus	2		HEAD / FACE
Pronator teres	2	54*	Fibularis brevis	1		Occipitalis	2
Flexor carpi ulnaris	2	54*				Frontalis	2
Flexor carpi radialis	2	54*				Orbicularis oculi	2
Flexor digitorum superf.	2	54*				Procerus	1
Flexor digitorum profund.	2	54*				Levator labii superioris	1
Flexor pollicis longus	1	54*				Levator anguli oris	1
Palmaris longus	1					Depressor anguli oris	1
Pronator quadtratus	1					Depressor labii inferioris	1
HAND			FOOT			Orbicularis oris	1
Flexor pollicis brevis	1		Extensor digitorum brevis	1		Buccinator	1
Abductor pollicis brevis	1		Extensor hallucis brevis	1		Risorius	1
Opponens pollicis	1		Abductor hallucis	1		Zygomaticus major/minor	1
Adductor pollicis	1		Abductor digiti minimi	1		Superior rectus	1
Flexor digiti minimi	1		Flexor digitorum brevis	1		Medial rectus	1
Abductor digiti minimi	1		Quadratus plantae	1		Lateral rectus	1
Opponens digiti minimi	1		Lumbricals	1		Inferior rectus	1
Palmaris brevis	1		Flexor hallucis brevis	1		Superior oblique	1
Lumbricals	1		Adductor hallucis	1		Inferior oblique	1
Dorsal interossei	1		Flexor digiti minimi brevis	1		Masseter	1	NI
Palmar interossei	1		Dorsal interossei	1		Temporalis	1	NI
			Plantar interossei	1		Medial pterygoid	1
						Lateral pterygoid	1
						Genioglossus	1	34*
						Hyoglossus	1	34*
						Styloglossus	1	34*

[1] Authors’ contributions: Celeste Michelle Pilato - Data collection and analysis, statistical analysis, text writing and editing. Melissa Sue Walker - Data collection, text writing, generating figures. Andrea M. Nguyen - Data collection, text writing and editing. McKay Elizabeth Hanna - Data collection, text writing. Scott Lanxing Huang - Data collection, text writing. Erika Morgan Lutins - Data collection. M. Alex Meredith - Course director, Data collection, analysis and archiving, statistical analysis, contributed to writing/editing the text and generating figures. Peter Jacob Haar - Radiologic advice, generated radiologic figure and legend. Mathula Thangarajh - Neurology advice, edited/reviewed text/figures. Hope Theresa Richard - Pathology advice, edited/reviewed text/figures. Woon Nam Chow - Pathology advice, Data collection, performed Pathology assays and photomicroscopy, edited/reviewed text/figures.

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Dystrophic muscle distribution in late-stage muscular dystrophy

ABSTRACT