- Tarsal tunnel syndrome refers to entrapment of the posterior tibial nerve as it passes through the tarsal tunnel in the ankle. Common symptoms include pain, numbness and tingling in the foot. - Causes of tarsal tunnel syndrome include ganglion cysts, bone deformities, varicose veins, space-occupying lesions, and muscle or structural abnormalities that compress the nerve. - Radiological imaging techniques like ultrasound and MRI can identify potential compressive elements, assess nerve damage, and help determine appropriate treatment which may be conservative therapy or surgery.

1. Radiological imaging of Tarsal tunnel syndrome.
Dr/ ABD ALLAH NAZEER. MD.

2. Tarsal tunnel syndrome (TTS) refers to an entrapment
neuropathy of the posterior tibial nerve or of its branches
within the tarsal tunnel. This condition is analogous
to carpal tunnel syndrome. While carpal tunnel syndrome
is usually bilateral, tarsal tunnel syndrome is unilateral.
For better understanding of normal anatomy of tarsal
tunnel, please refer article - "tarsal tunnel".
Clinical presentation
The most common symptoms are pain and parasthesia in
the toes, sole, or heel and the main finding at physical
examination is the Tinel sign (distal parasthesia produced
by percussion over the affected portion of nerve).
Electromyography and nerve conduction studies are useful
in confirming the diagnosis.

3. Pathophysiology
Tarsal tunnel syndrome is a compression neuropathy of the
tibial nerve that is situated in the tarsal canal. The tarsal canal
is formed by the flexor retinaculum, which extends posteriorly
and distally to the medial malleolus.
The symptoms of compression and tension neuropathies are
similar; therefore, differences in these conditions cannot be
simply identified by the symptoms alone. In certain instances,
compression and tension neuropathies may coexist.
The double-crush phenomenon originates from work published
by Upton and McComas in 1973. The hypothesis behind this
phenomenon may be stated as follows: Local damage to a
nerve at one site along its course may sufficiently impair the
overall functioning of the nerve cells (axonal flow), such that
the nerve cells become more susceptible to compression
trauma at distal sites than would normally be the case.

4. Aetiology
idiopathic (50% cases)
ganglion cysts
bone deformity after calcaneal fractures
varicosities
tenosynovitis of the flexor tendons
tumours (e.g. neurilemmoma , lipoma)
accessory or hypertrophied abductor hallucis muscle
synovial hypertrophy
hind-foot valgus
post-traumatic fibrosis
os trigonum

5. - clinical findings:
- patients may note pain when the ankle is placed in
extremes of dorsiflexion (from nerve tension);
- patients note pain, parasthesia, foot numbness, and in
somes cases atrophy of foot intrinsic;
- pain will radiate along the plantar side of the foot,
sometimes up into the calf;
- positive Tinel sign behind medial malleolus;
- manual compression for 30 sec. may reproduce
symptoms;
- consider performing 2 point discrimination test both on
medial and lateral sides of the foot (and opposite foot);
- if the 2 point discrimination is increased on one side
of the foot, it may indicate which branch of the plantar nerve is
compressed;
- in most cases, symptoms will be improved w/ rest;

6. US imaging
To obtain a reliable outcome, US imaging of the tarsal tunnel and the
peripheral nerves must be performed by an experienced operator, who
is familiar with normal and pathological US findings. Top-of-the-range
US equipment including a high frequency probe is required.
Gray-scale and color Doppler US imaging starts with axial scans of the
proximal and distal tarsal tunnel on the medial side of the foot arch
and with a systematic study of the tibial nerve, the two plantar nerves
and the inferior calcaneal nerve. The patient should be in the lateral
decubitus position.
US Tinel test should be carried out by tapping over the nerve to elicit
symptoms, as a positive US Tinel sign is suggestive of a positive
diagnosis of Posteromedial tarsal tunnel syndrome, particularly when
the symptoms are linked to possible compression elements. In some
cases, the US Tinel sign may be the only positive sign in the absence of
compression elements or neuropathy. In case of pathological findings,
the nerve should be further studied in the longitudinal plane to
confirm previous findings.

7. US examination also includes a systematic study with the patient in the
standing position during limb loading using axial scans of the proximal
tunnel and the distal tunnel. The following two conditions should be
investigated:
Compression caused by bone disorders linked to static foot disorders,
including compression by the medial process of the talus in valgus flat
foot, which leads to pushing and stretching of the nerves;
Dilation of the plantar veins in the distal tarsal tunnel (vein diameter
>5 mm) when the patient is in the standing position. Venous dilation
should be suspected in the presence of positive US Tinel sign caused by
compression of the veins using the US probe or if the symptoms improve
when the patient is wearing Class II support soaks.
US can detect muscle atrophy and significant fatty infiltration linked to a
neurogenic pathology. In this case, comparison with the muscles of the
contralateral foot is essential. If the patient has a disease affecting the
nerve to the abductor of the fifth toe, a comparative assessment of the
abductor muscles of the fifth toes may show atrophy and hyperechoic
appearance of the affected foot and thereby confirm the diagnosis.

8. MRI
MR imaging clearly depicts the bones,
soft-tissue contents, and boundaries of
the tarsal tunnel as well as the different
pathologic conditions responsible for
tarsal tunnel syndrome.
MR imaging can also aid in determining
whether treatment should be
conservative (e.g. tenosynovitis) or
surgical (e.g. space-occupying lesions).

9. Posteromedial tarsal tunnel syndrome of the right foot during limb loading. US
imaging and MRI show a flexor digitorum accessories longus muscle of the toes
(FDAL) in the tarsal tunnel, satellite of the tibial nerve (TN), and plantar nerves (LPN,
MPN). After surgical removal of the accessory muscle, symptoms disappeared

10. Posteromedial tarsal tunnel syndrome of the right foot during limb loading.
Voluminous accessory soleus muscle (AS) in contact with the tibial nerve (arrow) in the
proximal tarsal tunnel of the right foot. There is no accessory muscle in the left foot

11. Posteromedial tarsal tunnel syndrome of the left foot. Comparative coronal
imaging of the distal tarsal tunnel shows significant hypertrophy of the
abductor hallucis muscle of the left foot causing plantar nerve entrapment

12. US shows a large epineural ganglion cyst adjacent to the tibial nerve (arrows)

13. Recurrent posteromedial tarsal tunnel syndrome after decompression. US axial scan and power
Doppler US of the proximal and distal tarsal tunnel show a large mass of vascularized scar tissue
at power Doppler US (arrowheads) in contact with the tibial nerve and the plantar nerves

14. Heel pain resulting from calcaneal fractures. US imaging shows the bones (arrow) in contact with the
inferior calcaneal nerve (ICN) in the distal tarsal tunnel. The image reveals atrophy and fatty
infiltration of the abductor muscle of the fifth toe (ABD V). CT shows a bone fragment on the medial
surface of the heel. MRI reveals contact between the bone fragment and fibrosis entrapping the nerve
thereby confirming atrophy and fatty infiltration of the abductor muscle of the fifth toe

15. Posteromedial tarsal tunnel syndrome. At US imaging, the tarsal tunnel appears normal, but a schwannoma
(arrows) is detected on the tibial nerve in the distal third of the leg. Diagnosis was confirmed by MRI

16. A schwannoma (arrows) is identified within the tarsal tunnel on (4a) T1 weighted sagittal and (4b) fat-
suppressed T2 weighted axial images. Note that unlike the fluid-signal intensity ganglion seen in (2a,2b),
this abnormality demonstrates soft-tissue signal intensity on both T1- and T2-weighted images.

17. MRI showing trapped and thickened nerve with tarsal tunnel syndrome.

18. (5a) This patient with symptoms of posterior tibial neuropathy was found to have varicosities
(arrows) within the tarsal tunnel, well seen on this fat-suppressed T2-weighted axial image.

19. Axial T1-weighted (a), fat-suppressed T2-weighted (b), and Gd-enhanced fat-suppressed T1-
weighted (c) MR images demonstrate varicose veins (white arrow) within the tarsal tunnel,
between the flexor digitorum longus (arrowhead) and flexor hallucis longus tendons (black arrow).

20. A sagittal A. SE 600/20 magnetic resonance image of dilated posterior tibial veins and
varicosities demonstrates a mass composed of multiple rounded and tubular intermediate
signal intensity structures that extends from the posterior ankle, through the tarsal
tunnel, and into the plantar soft tissue of the forefoot. On 6, an axial SE 2000/80 magnetic
resonance image, the mass is of high signal intensity and completely fills the tarsal tunnel.

21. MR imaging of tarsal tunnel
syndrome. a, b Axial T1WI (a)
and spin-echo T2WI (b)
demonstrate a lipoma
(arrowheads) in the upper
tarsal tunnel, compressing the
posterior tibial nerve
(arrows). c, d Axial T1WI (c)
and spin-echo T2WI (d)
demonstrate a ganglion
(arrowheads) in the lower
tarsal tunnel, possibly
compressing the lateral
plantar nerve (short arrow).
The medial plantar nerve is
not well visualized. The medial
calcaneal nerve (long arrow) is
well depicted. Both patients
had a tingling sensation in the
foot. AH abductor hallucis
muscle.

22. Ganglion cyst with tarsal tunnel syndrome. A T1 weighted axial
image and (1b) fat-suppressed T2 weighted sagittal image.

23. Tarsal tunnel
syndrome
secondary to
ganglion cyst. Axial
T2-weighted MR
image reveals a
ganglion cyst (*)
interposed between
the flexor digitorum
longus (d) and
flexor hallucis
longus (h) tendons
and abutting the
adjacent
neurovascular
bundle (arrow).

25. Ankle Tarsal Tunnel Ganglion.

26. Tarsal tunnel syndrome with flexor digitorum accessorius longus muscle.

27. T1-weighted sagittal (A) and axial (B) and sagittal fast spin-echo T2-weighted fat-suppressed (C) magnetic resonance
imaging of the left ankle showing neurofibroma in the tarsal tunnel. The well-circumscribed ovoid mass (asterisks) in
the tarsal tunnel is isointense to skeletal muscle on T1-weighted images (A, B). The neurofibroma is centrally
hypointense (arrows) on the T1-weighted images (A, B) and peripherally hyperintense (arrowheads) on the T2-
weighted image (C), consistent with central fibrosis and peripheral myxomatous composition.

28. Coronal and sagittal magnetic resonance images of the left ankle, which shows iso-signal intensity
on the T1-weighted (A) and strong enhancement on the Gadolinium enhanced images (B). Note its
relation to the posterior tibial nerve and the ovoid soft tissue mass with well formed capsule.

30. Thank You.