Cutaneous sural nerve injury after lateral ankle sprain

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Cutaneous sural nerve injury after lateral ankle sprain: A case report
Published on Diagnostic Imaging (http://www.diagnosticimaging.com)
Cutaneous sural nerve injury after lateral ankle sprain: A case
report
February 26, 2008
By Vijay Jorwani, MD [1], Kathleen Weber, MD [2], and Simon Lee, MD [3]
Our case report demonstrates the importance of conducting a thorough neurological examination in
the evaluation of lateral ankle sprain. The patient, a dancer, reported an inversion injury to his ankle
that was associated with lateral ankle pain, numbness, and paresthesia. The patient had positive
Tinel test results over the distal portion of the leg in the distribution of the sural nerve. The diagnosis
was a grade 1 lateral right ankle sprain complicated by an injury to the sural nerve. Treatment
included scheduled anti-inflammatory medication and limited icing of the ankle. The patient returned
1 week later and reported significant improvement; after 1 month, he had returned to full activity.
Knowledge of sural nerve anatomy is essential for examining physicians to make this diagnosis. (J
Musculoskel Med. 2008;25:126-128)
ABSTRACT: Our case report demonstrates the importance of conducting a thorough neurological
examination in the evaluation of lateral ankle sprain. The patient, a dancer, reported an inversion
injury to his ankle that was associated with lateral ankle pain, numbness, and paresthesia. The
patient had positive Tinel test results over the distal portion of the leg in the distribution of the sural
nerve. The diagnosis was a grade 1 lateral right ankle sprain complicated by an injury to the sural
nerve. Treatment included scheduled anti-inflammatory medication and limited icing of the ankle.
The patient returned 1 week later and reported significant improvement; after 1 month, he had
returned to full activity. Knowledge of sural nerve anatomy is essential for examining physicians to
make this diagnosis. (J Musculoskel Med. 2008;25:126-128)
Injury to the sural nerve in association with lateral ankle sprain rarely is mentioned in the literature.
However, this injury may occur more frequently than commonly thought, and it may be an
underdiagnosed and mistreated component of ankle sprains.1
In this article, we offer a case report of a patient with sural nerve injury after ankle sprain and a
discussion of the implications for diagnosis and treatment. The case demonstrates the importance of
conducting a thorough neurological examination in the evaluation of the common lateral ankle
sprain. We also illustrate the potential management pitfalls.
CASE REPORT
Presentation and history
A 25-year-old performer for a premier dance show reported an inversion injury to his right ankle that
was associated with lateral ankle pain. Seven days later, numbness and tingling began to develop in
his right heel and the lateral aspect of his right foot. When the patient was initially evaluated 11 days
after the injury, he reported continued numbness in the right heel and lateral ankle region, as well as
pain around the lateral malleolus. The patient had been unable to perform and was limiting his
activity because of the numbness. He denied any past medical or surgical history.
Evaluation
The initial examination revealed an athletic, well-conditioned man in no acute distress but with a
slightly antalgic gait. Inspection of the ankle showed mild swelling over the lateral right ankle.
Palpation revealed mild pain at the anterior talofibular ligament but no pain over the calcaneofibular
ligament, peroneal tendon, navicular, bifurcate ligament, base of the fifth metatarsal, or proximal
fibula.
Results of the squeeze test were negative; anterior drawer testing revealed pain with stress but no
laxity (Table). The patient had mild loss of range of motion of the ankle; motor testing of L3 through
S1 showed 5/5 strength. The patient had positive Tinel test results over the distal portion of the leg
Page 1 of 4
Cutaneous sural nerve injury after lateral ankle sprain: A case report
Published on Diagnostic Imaging (http://www.diagnosticimaging.com)
in the distribution of the sural nerve and numbness on examination of the right heel and lateral right
foot. Slump, straight-leg raise, cross-straight leg, and FABER (flexion, abduction, and external r
otation) test results were negative.
Radiographs of the right ankle showed an intact mortise and no evidence of osteochondritis
dissecans or acute fracture. A previous avulsion fracture was noted at the distal medial malleolus,
and an anterior talar osteophyte was seen. The diagnosis was a grade 1 (mild) lateral right ankle
sprain, complicated by an injury to the sural nerve.
Follow-up
Treatment involved scheduled anti-inflammatory medication and icing of the ankle for no more than
10 minutes 4 times per day. The patient was restricted in his dance to no jumping, landing, or
pushing-off of the right foot. He began a home-exercise program to maintain full ankle range of
motion. Bracing initially was not advised to avoid potential compression injury to the sural nerve.
The patient returned to the office 1 week later and reported significant improvement in his
symptoms. He noted no pain and only mild numbness and tingling when bearing weight on the right
heel. Examination results were markedly improved, with no tenderness or swelling. A Tinel test
reproduced mild symptoms of heel tingling. There was mild loss of eversion at the right ankle and
otherwise normal ankle motion.
The patient was permitted to return to dancing with the use of an ankle brace during performances
for the following 10 to 14 days. After 1 month, the patient had complete resolution of all symptoms
and had returned to full activity.
DISCUSSION
Anatomical course
The sural nerve is a purely sensory nerve of the lower extremity; its fibers originate in the S1 and S2
nerve roots.1 The sural nerve arises from the tibial nerve 3 to 5 cm distal to the knee joint in the
popliteal fossa and later receives a communicating branch of the common peroneal nerve. It
descends midline, between the 2 heads of the gastrocnemius muscle and becomes subcutaneous at
the distal one third of the leg.2 The nerve proceeds along the lateral margin of the Achilles tendon,
posterior to the lateral malleolus with the peroneal tendons, and along the dorsolateral aspect of the
foot.
The anatomical course of the sural nerve corresponds to its cutaneous innervation, which includes
the lateral lower third of the lower extremity, the lateral heel, and the dorsolateral aspect of the foot
up to the base of the fifth toe.2 The nerve may be injured at any point along this course.
Underdiagnosed?
As a group, nerve injuries of the foot and ankle in athletes are uncommon but may be
underdiagnosed.3 The sural nerve is the only nerve in the body in which the most common cause of
injury is iatrogenic. Nerve grafting or biopsy of the sural nerve can cause numbness in its
distribution, as well as painful neuromas at the site of damage that may require resection.
Peripheral nerve injuries
Page 2 of 4
Cutaneous sural nerve injury after lateral ankle sprain: A case report
Published on Diagnostic Imaging (http://www.diagnosticimaging.com)
Our patient’s sural nerve neuropathy was caused by a lateral ankle sprain. The pathophysiology in
this case probably involved traction to the nerve (Figure) analogous to that in traction-type injuries
seen in the brachial plexus. Ensuing inflammation to the nerve itself may have resulted in our
patient’s numbness and tingling.
Figure – This photograph of a
healthy ankle shows the anatomy of the sural nerve, as well as the site of injury and symptoms
described in this case. The course of the sural nerve corresponds to its cutaneous innervation.
Nerve entrapment–type injuries have been divided into 3 clinical stages: in stage 1, patients have
pain and paresthesia at rest and at nighttime; stage 2 involves paresthesia, numbness and,
occasionally, muscle weakness that occur during daytime; patients with stage 3 nerve injuries may
complain of constant pain, muscle atrophy, and permanent sensory loss.1 The natural history of
peripheral nerve injuries may be unpredictable.
A neurological examination of the ankle and foot always should be undertaken during the physical
examination. Testing may reveal sensory deficits along the distribution of the sural nerve. The Tinel
test with percussion along the course of the nerve may help delineate the location of injury and may
reproduce paresthesia.
Differential diagnosis/imaging
The differential diagnosis for lateral ankle pain and paresthesia includes lateral ankle sprain, chronic
ankle sprain, peroneal tendinitis, osteochondritis dissecans of the talus, fifth metatarsal fracture,
lateral malleolus fracture, sinus tarsi syndrome, Achilles tendinitis, radicular symptoms referred from
the lower back, complex regional pain syndrome, and sensory nerve injury involving the superficial
peroneal nerve or sural nerve. Radiographs help rule out fracture, osteochondromas, and myositis
ossificans as compounding diagnoses in patients who have neurological deficits.
Nerve conduction studies may be used to confirm the diagnosis when the presence of sural
neuropathy is questionable; to rule out proximal nerve pathology, such as nerve root compression;
or when symptoms persist. If nerve compression caused by a Baker cyst or bone spur is suspected,
CT or MRI may be helpful.
Successful treatment
Our patient had a favorable outcome because the diagnosis was prompt and treatment was careful.
Initial treatment should be conservative but with some considerations kept in mind. To avoid
compression or thermal injury to the sural nerve, icing was limited to 10 minutes and ankle taping
and bracing were not allowed until the patient’s neuropathy showed significant improvement.
Scheduled NSAIDs and an initial reduction in activity were used to avoid aggravating the inflamed
nerve. The patient immediately began exercises to preserve range of motion and followed with
stepwise rehabilitation of his lateral ankle sprain.
A review of the literature suggests caution when patients are fitted with casts and shoes. Chronic
symptoms include intractable exercise-related calf pain and prolonged numbness. These cases may
involve sural nerve entrapment and require surgical neurolysis or decompression.4
Case reports also have mentioned the use of amitriptyline and clonazepam in managing pain
associated with sural nerve injury. In the current case, the patient noted successful analgesia with
scheduled NSAIDs.
References:
References
Page 3 of 4
Cutaneous sural nerve injury after lateral ankle sprain: A case report
Published on Diagnostic Imaging (http://www.diagnosticimaging.com)
1. 1. Hirose CB, McGarvey WC. Peripheral nerve entrapments. Foot Ankle Clin. 2004;9:255-269.
2. 2. Refaeian M, King JC, Dumitru D. Isolated sural neuropathy presenting as lateral ankle pain.
Am J Phys Med Rehabil. 2001;80:543-546.
3. 3. Schon LC, Baxter DE. Neuropathies of the foot and ankle in athletes. Clin Sports Med.
1990;9:489-509.
4. 4. Fabre T, Montero C, Gaujard E, et al. Chronic calf pain in athletes due to sural nerve
entrapment: a report of 18 cases. Am J Sports Med. 2000;28:679-682.
Source URL:
http://www.diagnosticimaging.com/articles/cutaneous-sural-nerve-injury-after-lateral-ankle-sprain-ca
se-report
Links:
[1] http://www.diagnosticimaging.com/authors/vijay-jorwani-md
[2] http://www.diagnosticimaging.com/authors/kathleen-weber-md
[3] http://www.diagnosticimaging.com/authors/simon-lee-md
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