How To Address Ganglionic Cysts In The Tarsal Tunnel
Tarsal tunnel syndrome is an entrapment of the posterior tibial nerve or its branches within the tarsal tunnel.1 This syndrome is most frequently unilateral as opposed to carpal tunnel syndrome in the upper extremity, which is typically bilateral.2 Keck and Lam first described the term “tarsal tunnel syndrome” in 1962.3,4
Malaisé first described the clinical signs and symptoms of tarsal tunnel syndrome in 1918. Some of the symptoms include numbness or tingling in the soles of the feet and toes or a burning pain in the ankles.5 A sensation of tightness, cramping pain and worsening of symptoms with prolonged standing have all been associated with tarsal tunnel syndrome.6
Diagnosing this syndrome can be difficult as the symptoms of nerve compression are described in a vague way and may mimic other pathologies of the foot and ankle. Often the patient’s own misconception of his or her multiple foot problems adds to the difficulty.7 Adjunctive methods often aid in both diagnosing the syndrome and differentiating the etiology.
When it comes to proper treatment, the etiology of tarsal tunnel syndrome is just as important as making the correct diagnosis. Using both nerve conduction velocity (NCV) testing and visualizing the area with either ultrasonography or magnetic resonance imaging (MRI) can be key in the physician’s ability to apply the appropriate treatment plan. Magnetic resonance imaging clearly depicts bones, soft tissue and boundaries of the tarsal tunnel, and can often reveal the specific pathology responsible for tarsal tunnel syndrome. This modality easily shows lesions of the synovial sheath, varicose veins and ganglions, which may all present in the tarsal tunnel and can cause the syndrome.1
What You Should Know About Space-Occupying Lesions And Entrapment Neuropathies
One of the most frequently diagnosed neuropathies is related to the entrapment of the posterior tibial nerve and its branches within the tarsal tunnel. The symptoms of tarsal tunnel syndrome may be due to a number of local factors such as space–occupying lesions, trauma and systemic diseases. However, a large number of tarsal tunnel cases are idiopathic.
This article presents two case studies with both patients suffering with tarsal tunnel syndrome due to a ganglion, one originating from the flexor hallucis longus tendon and the other originating from the middle facet of the subtalar joint. Both cases presented with acute onset of unilateral neuropathy and pain.
In the following two case studies, ganglion cysts are the etiology of the patients’ symptoms. Stedman’s Medical Dictionary (27th edition) defines a ganglion as “a cyst containing mucopolysaccharide-rich fluid within a fibrous tissue, muscle, bone or a semilunar cartilage.” The ganglions usually originate “from a tendon sheath in the hand, wrist, foot or can be connected with the underlying joint.”
Conservative measures may not be the best options for managing and treating tarsal tunnel syndrome when it is caused by a space-occupying lesion such as a ganglion cyst. The use of strapping, orthotics or removable walking boots often fails because these modalities do not address the etiology, and the ganglion remains within the tarsal tunnel.
While one may consider many techniques, the basic purpose of tarsal tunnel surgery is to release the flexor retinaculum and dissect the fibro-osseous tunnel that makes up the tarsal tunnel. The specific structures one would release are the fascia envelopes of the abductor hallucis muscle, tibial nerve, medial and lateral plantar branches and the calcaneal branch.
The degree of dissection depends on the anatomical makeup of the individual and the degree of entrapment. When it comes to any space-occupying lesion you find in the exploration of the tarsal tunnel (a ganglion in our case), you would dissect and remove it with care so as to not damage normal structures of the area.
When a space-occupying lesion is involved with tarsal tunnel syndrome, surgery may be the only option to decrease pain and halt or reverse nerve damage. Although surgical release is not effective in all cases, Gondring, et al., found complete relief of symptoms in 85 percent of 68 feet in their study in 2003.5
Case Study One: When A Patient Has Acute Numbness Of The Toes
A 41-year-old male presented with a complaint of acute numbness of his left toes. The patient reported that the numbness began two to three months prior to his presentation. He noted the numbness was constant in his first to third or fourth toes. He also had tingling in his feet but denied shooting pains. The patient initially presented to his primary care physician who had ruled out diabetes. He could not associate any traumatic or other event or episode that preceded the onset of his symptoms. However, the patient did recall recently hearing a pop when walking barefoot in his kitchen. He stated that since that time, he had more burning in his foot and felt the numbness had been worse.
The patient’s medical history was significant for hip cysts and back pain. His only medication was celecoxib (Celebrex, Pfizer). He had no known food or drug allergies.
The lower extremity examination revealed fully intact neurovascular status of the right (uninvolved) foot. Examination of the left foot revealed decreased neurological status with absent protective sensation as tested with the Semmes-Weinstein 5.07 monofilament under the first and second digits. This was intact on the other digits but the intensity of sensation was decreased at the first and second metatarsophalangeal joint levels, and proximal to the medial malleolar level. The patient had diminished sharp/dull sensation on the left foot as well and this was greatest at the first and second toes.
The muscle strength was 5/5 for all groups tested and the muscle tone was normal. There was no Tinel or Valleix sign elicited with percussion of the tibial nerve. No ecchymosis, calor or erythema was present at any site. The patient had no pain with range of motion of the metatarsophalangeal joints (MPJs), subtalar joint or ankle joint bilaterally.
We performed electromyography/NCVs of the left foot. This revealed left posterior tibial motor, mild latency delay, diminished amplitude and normal conduction velocity. The left posterior tibial motor recording at the lateral plantar nerve of the left foot demonstrated delayed latency with diminished amplitude. The left posterior tibial motor recording at the medial plantar nerve demonstrated a much delayed latency and diminished amplitude. Recording at the ankle and stimulating at the medial plantar nerve on the left foot also showed a delayed latency with diminished amplitude. Stimulating at the lateral plantar nerve of the left foot and recording at the posterior tibial at the ankle showed a much delayed latency with diminished amplitude. The left posterior tibial F-wave was delayed in comparison to the left peroneal F-wave.
The findings were consistent with a cyst in the foot although the report stated that findings could also be suggestive of a more proximal involvement of the sciatic/S1 nerve.
The radiographic evaluation revealed no abnormalities. We obtained a MRI of the left foot using a 1.0 Tesla magnet, including T1-and T2- weighted images in the long and short axis of the foot. We identified a large multiseptated, fluid-containing cystic structure, which extended along the inferior aspect of the sustentaculum tali along the inferior surface of the flexor hallucis longus tendon. The structure was approximately 37 x 12 x 20 mm in size. The findings were compatible with a ganglion of the flexor hallucis longus tendon sheath producing impingement of the posterior tibial neurovascular bundle at the bifurcation of the medial and plantar cutaneous nerves of the distal tarsal tunnel. There was mild synovitis of the posterior tibialis, flexor hallucis longus and flexor digitorum longus tendon sheaths.
Key Surgical Insights
The surgical procedure consisted of making a 7 cm curvilinear incision posterior to the palpable posterior tibial pulse, approximately 1 cm, and extending it distal above the abductor hallucis muscle belly and plantar to the navicular tuberosity toward the porta pedis. After significant dissection, a large fluid-filled mass was present along the medial wall of the calcaneus and was approximately 4 x 2 cm in size. The surgeon incised the encapsulated mass to allow for complete excision. A significant amount of straw-colored, thick, gelatinous fluid exuded after complete removal of the mass. The surgeon performed closure and placed a transcutaneous light suction drain within the wound due to the large dead space created.
The patient received an injection of a mixture of 0.5% marcaine plain and dexamethasone sodium phosphate 4 mg/mL at the site. The patient also wore a sterile compressive dressing and a below-knee posterior splint.
The Pathology Consultants of Cleveland received the pathology specimen. The final diagnosis from the surgical pathology report confirmed a benign ganglionic cyst.
Case Study Two: A Patient With Pain And Numbness On The Ball Of The Foot
A 48-year-old male presented with a complaint of acute pain and numbness across the ball of his right foot. The patient reported that the symptoms started suddenly exactly two weeks and one day prior to presentation, and he had more pain with rest than with activity. He noted that he felt the numbness on his first three toes and part of the fourth toe on the affected foot. The patient denied any trauma to the foot that preceded any symptoms but admitted to a recent history of increased activity on an elliptical trainer in an old pair of basketball shoes. He denied any tingling or shooting pains. The patient denied any history of back problems.
The patient’s medical history was positive for inflammatory myopathy. His medications included 200 mg hydroxychloroquine sulfate (Plaquenil). He stated an allergy to naproxen (Naprosyn, Roche Pharmaceuticals), which caused a rash. His only surgical history was a repair of a cruciate ligament in his knee.
The lower extremity examination revealed fully intact neurovascular status to the left (uninvolved) foot. Examination of the right foot revealed decreased neurological status with diminished sharp-dull and light touch to the hallux, second, third and fourth digits. The vibratory sensation was intact. The Hoffman-Tinel sign was positive with percussion of the tibial nerve at the tarsal tunnel right. There was localized edema in the right foot overlying the tarsal tunnel region. There was no pain with range of motion of the ankle, subtalar joint or MPJs.
Radiographic evaluation revealed no abnormalities. We obtained a MRI after the patient was unresponsive to conservative therapy of mechanical support and antiinflammatory therapy. Routine MRI of the right foot included T1 and T2 weighted images in all planes. Within the tarsal tunnel posterior and medial to the flexor hallucis longus, we identified a tubular cystic structure that was T2 hyperintense and was 3.2 cm x 1.2 cm x 1.4 cm in size. It appeared to have originated from the middle facet under the sustentaculum tali.
A Guide To The Surgical Procedure
In regard to the surgical procedure, we initially made a 10 cm incision, beginning behind the medial malleolus over the palpable posterior tibial artery, and extending down to the plantar fascia region along and throughout the course of the neurovascular bundle. A palpable ganglion cyst deep in these tissues was present at the mid-aspect of the incision.
After deep dissection, the surgeon identified a large cyst approximately 3 cm in length and 1.5 cm in width, and the surgeon circumferentially separated it from the surrounding soft tissues. The cyst was overlying the tibial nerve and was slightly anterior to this nerve. A stalk from the cyst led down to the sinus tarsi region. We closed off the stalk with a suture and cut just superficial to the stalk so we could remove the cyst in toto.
After closing the wound, the surgeon injected an ankle block using 30 cm3 of 0.5% plain marcaine. The patient received a modified Jones dressing.
The Cleveland Clinic received the specimen. The diagnosis confirmed a ganglionic cyst.
Pertinent Perspectives On The Case Studies
These two cases offered interesting examples of when the etiology of tarsal tunnel is difficult to assess clinically. In both instances, the patients’ symptoms were quite severe and began very abruptly. Both patients had local deficits of sensation and one had a positive Tinel’s sign. The symptoms and findings were very general upon clinical examination and fell short of the information needed to properly diagnose and treat the patients.
We have detailed the importance of using accessory diagnostic tools in these instances. Timely and appropriate treatment of ganglion cysts within the tarsal tunnel causing nerve compression is vital and will limit the potential damage done to the nerve and the need for further intervention.
The diagnosis of tarsal tunnel syndrome must rely strongly upon the clinical presentation and evaluation. There is evidence to show that a patient has a statistically higher chance of a better outcome if the Tinel’s sign is positive.8 However, ganglions are not always palpable within the fibro-osseous tarsal tunnel. Accordingly, adjunctive imagery such as MRI and ultrasonography may be useful tools. Electrodiagnostic nerve conduction velocity studies may be another useful means to determine nerve latency.
When it comes to decreasing recurrence rates, complete surgical excision is the gold standard of treatment for space-occupying lesions within the tarsal tunnel.9 The aforementioned case studies provide examples of using both clinical examination and advanced imagery to diagnose tarsal tunnel syndrome.
Dr. Stock practices at the Cleveland Clinic in Cleveland.
Dr. Baxter completed her PGY1 year at the Cleveland Clinic followed by a surgical residency in Salt Lake City. She is currently doing a fellowship in Texas.
Dr. Herbert practices at the Cleveland Clinic.
Dr. Sferra is a foot and ankle orthopedic surgeon practicing at the Cleveland Clinic.
Dr. Burks is a Fellow of the American College of Foot and Ankle Surgeons, and is board certified in foot and ankle surgery. Dr. Burks practices in Little Rock, Ark.
Editor’s note: For related articles, see “A Closer Look At Tarsal Tunnel Syndrome” in the November 2003 issue, “Rethinking Tarsal Tunnel Syndrome” in the December 2004 issue or “Expert Insights On Peripheral Nerve Surgery For Tarsal Tunnel Syndrome” in the September 2003 issue. For other articles, visit the archives at www.podiatrytoday.com.
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