45-year-old male patient presented with a long-term painless swelling tumour in the back part of right thigh. No history of trauma or injury was recorded.
Voluminous multiloculated tubular lesion was detected tracking along the course of tibial nerve from the proximal tibia epiphysis to the distal third of the thigh (Figure 1).
It was connected to the proximal tibiofibular joint through a discontinuity of the posterior capsule and extends along the articular branch into the tibial nerve (tail sign) (Figure 2). There were no signs of osteoarthritis.
Distal portion of sciatic nerve and branch of tibial nerve to the popliteus muscle were also involved. Common peroneal nerve was spared (Figure 3).
It shows high signal on T2WI without contrast-enhancement. There is eccentric compression of tibial nerve fascicles (signet ring sign) (Figure 4)
Subclinical denervation of tibialis posterior, flexor digitorum longus and flexor hallucis longus muscles was detected on MRI, as high signal on T2WI representing oedema (Figure 5) and high signal tracts on T1WI representing fatty infiltration and atrophy (Leminen score 1-2) (Figure 6) [1]. The other muscles innervated by tibial nerve (medial and lateral heads of gastrocnemius, soleus and plantaris muscles were spared).
Patient remained asymptomatic, so conservative management was proposed.
Intraneural ganglion cysts are increasingly diagnosed benign cysts caused by accumulation of thick mucinous fluid within epineurium of peripheral nerves, encased in dense fibrous capsule [2-3].
Unifying articular theory proposes that intraneural ganglion cysts have a synovial origin [2].
They are formed from a capsular discontinuity of the joint secondary to direct or indirect trauma or degenerative changes. This defect allows articular fluid to follow the path of least resistance dissecting upwards within epineurium of articular branches with eccentric compression of fascicles [2-3].
Clinically, patients present with pain, paresthesias, weakness, muscle denervation and atrophy [2].
Common peroneal nerve is more commonly affected overall and ulnar nerve and its branches are the most frequent in upper extremity [2-3].
Intraneural ganglion cysts of the tibial nerve are extremely rare with only few cases reported in literature [4-5].
There is a classification of intraneural ganglion cysts of tibial nerve according to their extension: Limited to near the tibiofibular joint (grade 0), extension into the inferior geniculate articular branch that reach the medial condyle of tibia (grade 1), the popliteus muscle branch (grade 2), all the tibial nerve (grade 3) or into the sciatic nerve (grade 4) [].
On MRI, they appear as multiloculated tubular lesions tracking along the course of the nerve with eccentric compression of nerve fascicles (signet ring sign). They show homogenous high signal intensity on T2WI with or without peripheral contrast-enhancement [4-6].
In most cases, connection between intraneural ganglion cyst and proximal tibiofibular joint is depicted (tail sign). In confounding cases, MR arthrography can help in depicting this connection [6].
Signs of muscle denervation appear as high signal intensity on T2WI representing edema in subacute cases and fatty infiltration and atrophy on T1WI in chronic cases [2-3]. In cases of tibial nerve ganglion cyst, tibialis posterior, extensor digitorum longus and extensor hallucis longus muscles are affected [4-5]. Popliteus muscle is also affected if intraneural ganglion cyst extends to its branch [6].
Differential diagnosis includes cystic nerve sheath tumours (schwannoma), atypical Baker’s cyst, and extraneural ganglion cyst, intraneural lipoma and haematoma [2-3].
Extraneural ganglion cysts share the same origin in a discontinuity of capsular joint and may be present at the same time [2-3]. Characteristics of extraneural ganglion cyst that help in differentiation from intraneural ones are:
Patients with clinically relevant intraneural ganglion cysts are treated with surgery, which includes decompression of the nerve, disconnection of the articular branch and resection of the synovium. Less invasive alternatives include percutaneous decompression or ultrasonography-guided aspiration, with higher rates of recurrence [2-3].
Intraneural ganglion cyst of the tibial nerve in a subacute stage with muscular oedema and fatty infiltration
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MRI shows a multi-loculated, tubular T2 hyperintense lesion in the soft tissue at the posterior aspect of the right thigh, extending along a branch of the sciatic nerve (suspected to be the tibial nerve). The lesion demonstrates homogeneous signal characteristics, predominantly T2 hyperintensity, with relatively well-defined margins. A local “signet ring” appearance suggests that the lesion is located within the nerve sheath and can cause eccentric compression of the nerve bundles. Abnormal signals of the surrounding muscles are observed, with T2 hyperintensity in some muscle groups, indicating possible denervation changes. No obvious bone destruction or significant abnormal bony signal is noted in the periarticular soft tissues; no significant effusion or other notable abnormal findings are seen in the suprapatellar bursa or joint capsule.
Based on the tubular configuration of the lesion along the nerve path, its signal characteristics (T2 hyperintensity accompanied by a “signet ring” appearance), and local muscle denervation changes, an intraneural ganglion cyst is highly likely. The pathologic mechanism is often related to synovial fluid protruding from the joint and tracking retrogradely along the nerve sheath.
Such tumors can also originate from nerve tissue, but the mass typically appears solid or shows mixed solid-cystic signals, often with significant contrast enhancement. Purely cystic, tubular, multi-loculated structures that have a potential communication with the joint synovium are relatively rare in comparison.
Typically located in the popliteal fossa near the joint capsule; however, if the location or morphology is atypical, it should be included in the differential diagnosis. In this case, the lesion extends axially along the nerve with a distinct tubular form, which is more suggestive of an intraneural cyst.
Although it may connect with synovial fluid near the joint, it usually does not exhibit significant extension along the nerve sheath. There is often a clear fat plane between it and the nerve trunk, and muscle denervation changes are generally less pronounced than those seen with intraneural cysts.
Considering the patient’s age, clinical presentation (a long-standing painless mass), imaging characteristics (a multi-loculated tubular T2 hyperintense lesion along the tibial nerve with eccentric compression and denervation signals), and typical site of origin, the most likely diagnosis is Intraneural Ganglion Cyst of the Tibial Nerve. If clinical symptoms persist or worsen, or if further confirmation is necessary, ultrasound-guided aspiration or surgical exploration with pathological examination can be considered.
Treatment Strategy:
Rehabilitation and Exercise Prescription Recommendations:
Focus on immobilizing and protecting the affected limb, avoiding excessive weight-bearing and stretching maneuvers. Mild joint mobility exercises, such as active range-of-motion exercises for the ankle and knee joints, can be implemented to maintain joint flexibility. Perform exercises 1-2 times per day, 5-10 minutes each time, with intensity kept at a level that does not cause significant pain or fatigue.
Gradually increase lower limb strengthening by incorporating exercises such as ankle pumps and mild to moderate resistance training for calf muscles (for example, plantarflexion and dorsiflexion with resistance bands). Exercise frequency can be adjusted to 3-4 times per week, each session 15-20 minutes, maintaining a light to moderate intensity (around RPE 3-4).
Based on the patient’s specific condition, enhance weight-bearing and proprioceptive training, such as single-leg balance, squats, walking, or light jogging. Progress gradually, ensuring no nerve pain or significant discomfort. Sessions may be held 3-5 times per week, each lasting 20-30 minutes, and gradually increased according to tolerance.
If there is significant weakness or sensory impairment in the lower limb, a specialized rehabilitation therapist should develop a tailored exercise plan and closely monitor changes in nerve symptoms to prevent secondary injury from over-stretching. If there is poor postoperative wound healing or other complications, exercise should be paused or modified.
In summary, if there is no severe nerve dysfunction, minimally invasive or conservative treatment can be adopted; however, surgery may be considered if significant neurological deficits or muscle atrophy occur. Once the appropriate intervention is carried out, a patient and gradual rehabilitation program is beneficial in restoring or maintaining lower limb function.
This report provides a reference medical analysis based on the information provided and does not replace in-person consultation or professional medical advice. If you have further concerns or changes in your condition, please seek evaluation and guidance from a specialist promptly.
Intraneural ganglion cyst of the tibial nerve in a subacute stage with muscular oedema and fatty infiltration
