Miositis Vs Contractura Musculo Esternocleidomastoideo Elastografia Shear Wave: Análisis de un caso
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| 1-Galndula Parótidas Derecha Normal con Ganglio Reactivo Interno |
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| 2.-Glandula Parótidas Izquierda normal |
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| 3.-Adenomegalia Reactiva Derecha |
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| 4.-Doppler Adenomegalia Reactiva Derecha |
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| 5.-Elastografia Región Hiliar de Adenomegalia Reactiva |
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| 6.-Elastografia Cortical Adenomegalia Reactiva |
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| 7.-Elastografia Musculo Esternocleidomastoideo Derecho Engrosado |
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| 8.-Elastografia Musculo Esternocleidomastoideo Izquierdo Normal |
Valoración comparativa de Ambos Músculos.-
| Parámetro | ECM Derecho | ECM Izquierdo |
|---|---|---|
| Mediana SWE | 25.9 kPa | 24.7 kPa |
| Máximo SWE | 29.4 kPa | 31.4 kPa |
| Diferencia real | +1.2 kPa | — |
📌 La diferencia entre ambos músculos es leve y dentro del rango fisiológico para variaciones individuales y contractura leve.
Interpretación clínica
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El ECM izquierdo muestra elasticidad conservada, sin signos de rigidez aumentada ni disrupción estructural.
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La distribución de colores está dentro del rango normal (predominio de verde-azul).
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No hay evidencia ecográfica de miositis, contractura ni lesión.
Elastografía shear wave del músculo esternocleidomastoideo izquierdo. Se observan valores normales de rigidez con una mediana de 24.7 kPa. No hay evidencia de disrupción fibrilar ni aumento significativo de la dureza, hallazgos que apoyan el diagnóstico diferencial de contractura muscular unilateral (lado derecho) frente a una miositis
En esta entrada demostramos la utilidad de tener la posibilidad de usar la Elastografia Shear Wear para diferencial casos con diagnosticos diferenciales dificil de discernir
CASE BACKGROUND
Male patient, 24 years old, presenting with intense pain and contracture of the right sternocleidomastoid (SCM) muscle. The symptoms were noted on the same day as the ultrasound exam, immediately upon waking. He denies fever, chills, or general malaise.
PHYSICAL EXAMINATION
The right SCM muscle appears enlarged compared to the contralateral side, with a firm consistency and pain on palpation. At the time of examination, the patient was under intravenous analgesia.
ULTRASOUND FINDINGS
Ultrasound of the area reveals a hypoechoic appearance of the right sternocleidomastoid muscle, with myofibrillar dispersion/disorganization and increased thickness compared to the left SCM. Both parotid glands appear normal in shape, size, echogenicity, and homogeneity, with no sonographically detectable pathological lesions.
Additionally, multiple enlarged lymph nodes with increased Doppler flow are noted on the right side of the neck (Image 4).
Shear Wave Elastography (SWE) – Sternocleidomastoid Muscles
Both SCM muscles were assessed:
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Right SCM: median stiffness of 25.9 kPa
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Left SCM (non-affected side): median of 24.7 kPa
These values are consistent with muscle contracture and argue against myositis, since the latter typically presents with decreased SWE values. Inflammatory processes involving the SCM muscles are bacterial in 98% of cases, with Staphylococcus aureus responsible for 90%.
Neck CT Scan
Findings include diffuse enlargement of the right SCM throughout its course without evidence of space-occupying masses. Small nodules suggest lymph nodes.
Shear Wave Elastography (SWE) – Lymphadenopathy (Images 5–6)
Three measurements were taken at the hilar region and three at the nodal cortex:
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Hilar median SWE: 104 kPa
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Cortical median SWE: 75.3 kPa
(Cut-off for malignancy: 174 kPa)
Benign reactive nodes typically show SWE medians ranging from 8.2 to 14.8 kPa, while metastatic nodes range from 52.4 to 117.6 kPa.
CONCLUSION
The differential diagnosis between myositis and muscle contracture was evaluated. Given the similar SWE median values between both SCM muscles, the diagnosis of right-sided muscle contracture is favored, and myositis is ruled out, since the latter would present with significantly elevated stiffness values in kilopascals.
The findings also demonstrate a localized infectious process triggering regional lymph node reactivity.
Image Descriptions:
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Normal right parotid gland with internal reactive lymph node
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Normal left parotid gland
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Reactive right cervical lymphadenopathy
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Doppler image showing reactive right lymphadenopathy
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SWE – Hilar region of reactive lymph node
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SWE – Cortical region of reactive lymph node
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SWE – Thickened right SCM muscle
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SWE – Normal left SCM muscle
Shear Wave Elastography – Muscle Analysis
The muscle stiffness values are slightly elevated, not reaching the typical values seen in acute inflammatory myositis. The color distribution (predominantly green-blue) and preserved architecture do not suggest severe infiltration or myofibrillar rupture.
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Right SCM SWE: Median 25.9 kPa – consistent with muscle contracture.
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The echostructure and color map do not suggest acute myositis.
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Clinical correlation supports sudden-onset painful muscle contracture.
Comparative Muscle Assessment
| Parameter | Right SCM | Left SCM |
|---|---|---|
| SWE Median | 25.9 kPa | 24.7 kPa |
| SWE Maximum | 29.4 kPa | 31.4 kPa |
| Real Difference | +1.2 kPa | — |
📌 The difference between both muscles is mild and within the physiological range for individual variation or mild contracture.
Clinical Interpretation
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The left SCM shows preserved elasticity, with no signs of increased stiffness or structural disruption.
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Color distribution is within the normal range (predominantly green-blue).
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No ultrasound evidence of myositis, contracture, or lesion.
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Left SCM SWE: Median 24.7 kPa – normal muscle stiffness values, supporting the differential diagnosis of unilateral muscle contracture (right side) rather than myositis.
*In this post, we demonstrate the usefulness of having the possibility of using Shear Wear Elastography to differentiate cases with difficult to discern differential diagnoses.
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