Age / Sex : 23 / F

Age/Sex: 23/ F

Chief complaint: Incidentally detected findings on Ankle MR

Accessory soleus, Peroneous quartus

Discussion

Findings: The
origin and insertion sites of an accessory
soleus muscle vary. The muscle may arise from the proximal third of the fibular,
the oblique soleal line of the tibia, the aponeurosis of the normal soleus
muscle, or combinations of these structures. The insertion sites of the
accessory soleus muscle include the Achilles tendon and the superior and medial
surfaces of the calcaneus. MR image confirms that the abnormal tissue has
signal intensity characteristics identical to those of normal muscle, unless
intramuscular hemorrhage or normal muscle.

 The peroneus
quartus muscle, its site of origin may include the distal lateral portion
of the fibula and the peroneus brevis or longus muscle. The insertion site of peroneus quartus muscle   may
include the phalanges or the metatarsal bone of the fifth toe, the calcaneus,
the cuboid bone, and the lateral retinaculum of the ankle.

Differential Diagnosis: There are three other accessory muscles in the posterior
aspect of the ankle: flexor digitorum longus accessorius muscle,
peroneocalcaneus internus muscles, and tibiocalcaneus internus muscle. The last
of these, the tibiocalcaneus internus
muscle is often considered a variation of the accessory soleus muscle,
typically extending from the medial crest of the tibia to the medial surface of
the calcaneus.

Discussion: An
accessory soleus muscle appears to represent a frequent finding, especially on
MR imaging examination. Affected persons are commonly asymptomatic, although
soft tissue fullness or a mass and occasionally pain and swelling after
exercise may be seen, especially in teenagers and young adults. The diagnosis
of this accessory muscle can be provided by routine radiography, CT, and MR
imaging. Of these techniques, MR imaging appears to be best. Treatment of
symptomatic patients with an accessory soleus muscle includes fasciotomy of the
muscle sheath or excision of the muscle, owing to the belief that the condition
may predispose to a localized compartment.

 The
peroneus quartus muscle, also designated the peroneus accessorius, peroneus
externus, and peronues calcaneus externus
muscle, has been associated with chronic pain and swelling about ankle. Its
reported frequency, on the basis of results of cadaveric dissections, has
varied from approximately 6 to 22 per cent. When this accessory muscle is
present, the retrotrochlear eminence is often prominent, and the frequency of
pathologic abnormalities of the peroneal tendons increases. [Resnick D. et al,
Internal Derangements of Joints, 2^nd edition, volume 2 2202 -2203]

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Report of   

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Accessory
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