Why have an MMAT score?
Both the World Small Animal Veterinary Association and the American Animal Hospital Association recommend recording both a Body Condition Score (BCS), and a Muscle Condition Score (MCS) as part of routine examination data collection.
Although both the BCS and the MCS evaluate uniform muscle wasting due to disease or malnutrition, neither system evaluates whether or not patients have increased muscle mass, or when different parts of the body have different MCS scores. Further, neither system allows for reporting muscle tone, which is easily determined when palpating the patient’s muscle mass.
How does the MMAT score work?
The MMAT score is divided into 3 parts, one for each the forehindlimbs, the vertebral column, and the hindlimbs, and each region is assigned its own score. Scores range from emaciation at one end, to debilitating excess of either mass or tone at the other.
During your physical examination, palpate each the hindlimb musculature, back musculature, and shoulder region, assigning it a number based on the description in Table #1
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Table #1
How does the MMAT score work? (Cont.)
For example, a dog with normal muscle tone and an even distribution of muscle mass throughout the body – enough muscle mass to allow long leash walks and playing in the park – would receive a score of 4/4/4. A working Malinois with taut, strong, and robust musculature would receive a score of 5/5/5. A dog with chronic bilateral cruciate disease, with atrophy of the hind legs but over developed musculature in the front legs due to weight shifting, would receive a score of 5/4/3.
In addition, there may be variations in muscle mass or tone within a body region. For example, a dog with unilateral cruciate disease may score a 3 for one hind leg, but 4 for the opposite hind leg. For these cases, assign an average score for the overall musculature in that region, and flag that value with a hashtag (“#”) symbol. Thus, a dog with normal muscle mass overall, except for atrophy secondary to chronic left hindlimb cruciate disease would be assigned a score of 4/4/4#. The “#” alerts the reader that there is uneven muscle distributions, a separate notation about the hind limb musculature is contained in the medical notes.
Similarly, if there is variation in muscle tone within a region, then an asterix (“*”) is applied. For example, if the dog above had increased tone in the lumbar musclulature secondary to lower back pain, its score would become 4/4*/4#.
How to palpate for the MMAT score
To assess muscle mass, have the patient stand squarely and facing forward. Palpate the shoulder blade musculature, along the top of the back as well as the abdominal wall, and the hindlimb musculature over the pelvis and thighs.
Muscle tone can be assessed at the same time, noting any changes from when the patient is standing, compared to lying down.
Key areas to evaluate
Forelimbs
Shoulder blade musculature (infraspinatus and supraspinatus): How prominent is the spine of the scapula? A prominent scapular spine, one that can be pinched from the sides, indicates inadequate mass of the surrounding musculature. Adequate musculature allows the top of the scapular spine to be felt, but not the sides. Robust or athletic musculature results in the top of the scapular spine palpable only as the bottom of a trough surrounded by raised musculature on either side.
Because of the thickness of front limb fascia, most muscles will have a very firm tone or texture regardless of whether the patient is standing or lying down. The triceps should have firm but not excessive tone when the patient is standing, and relaxed loose tone when the patient is lying down.
Vertebral Column and Abdominal wall
Dorsal spinus processes (DSP): The tops of the dorsal spinous processes should be palpable along the midline of the thoracolumbar spine, but it should not be possible to pinch the DSP from the sides; DSP become more prominent as the surrounding musculature atrophies. The mammillary processes are bony prominences that are shorter and immediately lateral to the DSP on either side. They should not be palpable in dogs with normal epaxial muscle mass.
To assess mass, palpate the musculature down the length of the vertebral column, from the temporalis muscles of the skull to the last lumbar vertebra. Regions with focal pain or pathology may have focal atrophy.
Palpate both the epaxial muscles and the abdominal wall to assess tone. Epaxial muscles are firm due to overlying fascia, but normal tone also allows for full flexibility of the vertebral column. The abdominal wall should be firm and tucked upward, not soft and pendulous.
Hindlimbs and pelvis
Pelvis and thigh musculature: The cranial aspect of the ilial wings (hip bones) should be surrounded by musculature that prevents palpation of more than the edge of the ilium. If the concave aspect of the lateral ilium is palpable, there is a deficiency of gluteal muscle. Similarly, palpate the circumference of the thigh musculature, noting development of the quadriceps cranially, and the hamstring muscles caudally.
All pelvic and thigh muscles should feel engaged when standing but relaxed when lying down or offloading the leg being examined. No spasticity or fibrous tone should be appreciated.
See Table #2 with scoring illustrations
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Table #2
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