TY - JOUR
T1 - US diagnosis of sciatic nerve tumor proximal to gluteal fold
AU - Granata, Giuseppe
AU - Gasparotti, Roberto
AU - Paolasso, Ilaria
AU - Erra, Carmen
AU - Tsukamoto, Hiroshi
AU - Padua, Luca
PY - 2014
Y1 - 2014
N2 - High-resolution ultrasound (US) is a helpful technique for
the evaluation of peripheral nerves. It is now well accepted
that especially in nerve mononeuropaties the combination
of morphological data, obtained through US, and functional
data, obtained through electrophysiology, is the
appropriate way to reach the best diagnosis including
information for therapeutical decision. Literature data show
that US may crucially influence diagnosis and clinical care
in nerve tumors [1, 2]. However, nerve US has some limitations.
In particular the visualization of deep nerves is
difficult, especially in overweight people. This is the case
of proximal part of sciatic nerve that is commonly
detectable only distal to the gluteal fold. We report on a
48-year-old woman complaining of pain and electric
shocks radiated to sciatic course and trigger point in the
right gluteal region. Clinical examination showed only
mild right extensor hallucis longus weakness. Needle
electromyography of tibialis anterior, gastrocnemius, peroneus
longus was normal and mild chronic neurogenic
recruitment was observed in extensor hallucis longus. It
was suspected a right L5 radiculopathy but magnetic resonance
(MR) showed only a mild L5–S1 bulging that was
not considered the cause of symptoms. US of sciatic nerve
was then performed although the trigger point was in a
region where usually sciatic nerve is not detectable, proximally
to the gluteal fold. US was performed using a linear
6–10 and 10–18 MHz transducer and sciatic nerve was
bilaterally evaluated in distal–proximal direction starting
from the popliteal fossa. Right sciatic nerve was detectable
along all its course, even proximally to the gluteal fold
although with no optimal visualization. At the middle-third
of the gluteus a fusiform hypoechoic increase of nerve
volume was found. The maximum longitudinal diameter
was 2.5 cm and maximum antero-posterior diameter was
2.0 cm (max cross-sectional area 4.5 cm2). An accurate
evaluation of the US video clip suggested that the mass
raised from lateral fascicles sparing and dislocating
remaining medial fascicles (Fig. 1a, b). US and clinical
data suggested a sciatic nerve tumor, likely a schwannoma.
MR confirmed the lesion showing a partially preserved
fascicular structure, suggesting a schwannoma (Fig. 1c–f).
Surgical excision was refused by the patient and US
monitoring planned. Our case report confirms the usefulness
of US in the diagnosis of nerve tumors. US is not able
to clearly differentiate the type of nerve tumor but can
provide useful information to discriminate between the two
main types, schwannoma or neurofibroma [3–5]. Schwannoma
typically displaces the nerve fascicles and generally
is positioned eccentrically to the affected nerve segment.
Another typical feature especially of large lesions is the
presence of hyperechoic calcifications and internal degenerative
cystic foci. On the other side neurofibroma presents
as a concentric lesion that does not displace the fascicular
elements of the nerve but interferes with them (usually
fascicles are not detectable). Another typical sonographic
feature of this kind of tumor is the so-called ‘‘target sign’’
(layered aspect, with a hyperechoic centre and a peripheral
hypoechoic rim, best seen on transverse scans) [6]. Usually sciatic nerve is not detectable with US proximally to gluteal
fold but in our case the visualization of proximal part
of the nerve was possible because the patient was athletic,
skinny and the tumor was big. In general our case suggests
to perform US also in district where usually for anatomical
reasons nerves are not clearly or totally viewable, because
sometimes macroscopic nerve enlargement may be
detected.
AB - High-resolution ultrasound (US) is a helpful technique for
the evaluation of peripheral nerves. It is now well accepted
that especially in nerve mononeuropaties the combination
of morphological data, obtained through US, and functional
data, obtained through electrophysiology, is the
appropriate way to reach the best diagnosis including
information for therapeutical decision. Literature data show
that US may crucially influence diagnosis and clinical care
in nerve tumors [1, 2]. However, nerve US has some limitations.
In particular the visualization of deep nerves is
difficult, especially in overweight people. This is the case
of proximal part of sciatic nerve that is commonly
detectable only distal to the gluteal fold. We report on a
48-year-old woman complaining of pain and electric
shocks radiated to sciatic course and trigger point in the
right gluteal region. Clinical examination showed only
mild right extensor hallucis longus weakness. Needle
electromyography of tibialis anterior, gastrocnemius, peroneus
longus was normal and mild chronic neurogenic
recruitment was observed in extensor hallucis longus. It
was suspected a right L5 radiculopathy but magnetic resonance
(MR) showed only a mild L5–S1 bulging that was
not considered the cause of symptoms. US of sciatic nerve
was then performed although the trigger point was in a
region where usually sciatic nerve is not detectable, proximally
to the gluteal fold. US was performed using a linear
6–10 and 10–18 MHz transducer and sciatic nerve was
bilaterally evaluated in distal–proximal direction starting
from the popliteal fossa. Right sciatic nerve was detectable
along all its course, even proximally to the gluteal fold
although with no optimal visualization. At the middle-third
of the gluteus a fusiform hypoechoic increase of nerve
volume was found. The maximum longitudinal diameter
was 2.5 cm and maximum antero-posterior diameter was
2.0 cm (max cross-sectional area 4.5 cm2). An accurate
evaluation of the US video clip suggested that the mass
raised from lateral fascicles sparing and dislocating
remaining medial fascicles (Fig. 1a, b). US and clinical
data suggested a sciatic nerve tumor, likely a schwannoma.
MR confirmed the lesion showing a partially preserved
fascicular structure, suggesting a schwannoma (Fig. 1c–f).
Surgical excision was refused by the patient and US
monitoring planned. Our case report confirms the usefulness
of US in the diagnosis of nerve tumors. US is not able
to clearly differentiate the type of nerve tumor but can
provide useful information to discriminate between the two
main types, schwannoma or neurofibroma [3–5]. Schwannoma
typically displaces the nerve fascicles and generally
is positioned eccentrically to the affected nerve segment.
Another typical feature especially of large lesions is the
presence of hyperechoic calcifications and internal degenerative
cystic foci. On the other side neurofibroma presents
as a concentric lesion that does not displace the fascicular
elements of the nerve but interferes with them (usually
fascicles are not detectable). Another typical sonographic
feature of this kind of tumor is the so-called ‘‘target sign’’
(layered aspect, with a hyperechoic centre and a peripheral
hypoechoic rim, best seen on transverse scans) [6]. Usually sciatic nerve is not detectable with US proximally to gluteal
fold but in our case the visualization of proximal part
of the nerve was possible because the patient was athletic,
skinny and the tumor was big. In general our case suggests
to perform US also in district where usually for anatomical
reasons nerves are not clearly or totally viewable, because
sometimes macroscopic nerve enlargement may be
detected.
KW - sciatic nerve tumor
KW - ultrasound
KW - sciatic nerve tumor
KW - ultrasound
UR - http://hdl.handle.net/10807/62472
U2 - 10.1007/s10072-014-1811-8
DO - 10.1007/s10072-014-1811-8
M3 - Article
SN - 1590-1874
VL - 35
SP - 1627
EP - 1628
JO - Neurological Sciences
JF - Neurological Sciences
ER -