neurilemmoma is defined as " a neoplasm that arises from schwann cells of the cranial , peripheral , and autonomic nerves " .
clinically , these tumors may present as cranial neuropathy , abdominal or soft tissue mass , intracranial lesion , or spinal cord compression .
the terminology regarding neurilemmoma may be confusing with neurinoma , neurocytoma , peripheral glioma , perineurial fibroblastoma and schwannoma . today ,
they are the most common type of peripheral nerve sheath tumor ( pnst ) , but they are rarely found in deep peroneal nerve sensory branch9121617 ) .
we report an interesting case of neurilemmoma of deep peroneal nerve sensory branch that triggered sensory change with compression test on lower leg and induced changes on pre- and post - operative infrared ( ir ) thermographic images .
ir thermography was taken at 23. it is the first to document a case of thermal change arising from neurilemmoma with compression test .
a 52-year - old woman had complained of pain at lower back and right leg for 9 months .
a local clinician made a diagnosis of herniated lumbar disc ( hld ) and performed a pain block on the patient 's spine .
the symptoms persisted , however , and a mass sized approximately 2 cm by 2 cm was palpated on the lateral side of leg , between right side of tibia and fibula , about 3.5 cm proximal to lateral malleolus .
she was subsequently referred to our hospital . upon visiting our hospital , she initially presented with sensory change on the dorsal side of the right foot , particularly the big toe .
percussion of the mass caused severe pain at fibular area , dorsal side of the right foot , and the big toe .
no neurologic signs were examined except for sensory change with compression test and mild numbness at the fibula and dorsal area of foot .
ultrasonography of the lower extremity discovered an oval - shaped mass sized 1.42 cm by 0.77 cm by 1.12 cm , considered as probably benign pnst arising from the right deep peroneal nerve sensory branch ( fig .
after 1 month , the low back pain was relieved by medication , but right leg pain remained , and an excision of the mass was planned .
a computed tomography ( ct ) scan with contrast of the both lower extremities was taken , which revealed a soft tissue mass within the sensory branch of right deep peroneal nerve ( fig .
when the palpable mass was compressed , the patient complained of sensory change , severe pain on fibula ( upward from mass to below the knee ) and dorsal area of foot , especially on fibular area and big toe . at that time , a thermal change was found on ir thermograpy , 31.83 at fibular area , 31.45 at dorsal area : specifically , the temperature of the fibular area was elevated by 0.75 and dorsal area was decreased by 0.15 ( fig .
a vertical skin incision was made under spinal anesthesia , and sharp and blunt dissection was used to expose the mass .
gross identification demonstrated a mass sized 1.4 cm by 1.2 cm and shaped like a pigeon egg ( fig .
4 ) . the tumor capsule was incised parallel to the running direction of nerve , and totally enucleated , with special attention paid to deep peroneal nerve sensory branch in order to avoid damaging the nerve .
the patient complained of mild sensory change on dorsum of foot , which was relieved partially over 1 month and completely over 2 months of period .
when the excision site was compressed , temperature was 31.49 at fibular area , 31.32 at dorsal area ( table 1 ) .
there is no severe sensory change , except mild op wound pain , and thermal elevation like pre - op status .
the temperatures at dorsal foot area do not show any significant difference in pre- and post - op status .
neurilemoma , also known as schwannoma , is a common benign tumor of the peripheral nerve1119 ) .
neurilemmomas usually arise at the intracranial cavity but may be found on other sites of the body .
odom et al.14 ) reviewed previous literature and reported that schwannoma of the leg comprise about 7.09% of all cases .
the initial impression of our case was herniated lumbar disc ( hld ) , which was ultimately found to be incorrect .
there has been a previous case where a patient with schwannoma of the peroneal nerve presented with sciatica , which was initially misdiagnosed as hld13 ) .
this patient 's perceived sciatic pain or l5 dermatomal pain could have lead to the misdiagnosis . in our case ,
the patient underwent several sessions of pain block in a local hospital , and there was no clear sign of improvement of low back pain .
causes of nerve irritational symptom include hld , ischialgia , piriform muscle syndrome , polyneuropathy , pernoneal nerve trauma , pressure upon peroneal nerve due to wearing immobilization , fracture or expansive process in the region of tibial head , lipoma , ganglioma , synovial cysts from popliteal region , anatomic variability , and others14 ) , and differential diagnosis should be made after considering the innervation of the deep peroneal nerve .
the diagnostic modalities available for the differential diagnosis include ct scan , ultrasonography , magnetic resonance imaging , and electromyography , among other31420 ) .
simple radiographs are not of much value when a patient presents with neurologic symptoms . ultrasonography has been considered as a useful screening tool3 ) , but it is difficult to perform such costly examination from the onset .
this examination measures the change in temperature radiating from the body resulting from alteration of subcutaneous capillary blood flow .
thus , for the precise examination , it is important to maintain a constant temperature and environment in thermography laboratory .
this was first used by lawson in 1956 for the diagnosis of breast cancer8 ) and is now being used as a novel method objectively quantifying the subjective sense of pain2 ) . in order to minimize the errors , our thermography lab maintains temperature at 23 , we use difference between temperature of before and after compression of the lesion .
the ir thermograpy demonstrated thermographic changes when the neurilemoma induced sensory change with compression test on the fibular area , dorsal side of foot , and the big toe .
the area of thermographic change was found to be related to the path of deep peroneal nerve sensory branch . in hld accompanied by leg pain ,
hyperthermic regions resulting from local dilation arise on the posterior lumbar skin that correlates to anatomic site of the compressed nerve due to antidromic stimulation .
the information is transmitted to the recurrent meningeal nerve , or sinuvertebral nerve , located at the spinal cord , and consequently , the autonomic output caused by the reflex arc leads to local vasoconstriction and hypothermia28 ) . in our case , however , there was greater blood flow at the pain site , which further increased upon inducing sensory change with compression test , resulting in hyperthermia ( fig .
while the degree of pain intensified in accordance with compression test , vasodilation and increased temperature of the skin was observed , rather than hypothermia and vasoconstriction caused by sympathetic nerves as seen in hld .
this may be explained by autonomic dysfunction following nerve injury ( in this case , tumor growth on peroneal nerve sensory branch ) , including changes of the sympathetic tone and norepinephrine synthesis1 ) .
sympathetic nervous system usually induces vasoconstriction by secretion of adrenaline , but sometimes , the cholinergic fibers within the sympathetic nerves releases acetylcholine , which may cause vasodilation and diaphoresis1015 ) .
the former may be more significant in hld , whereas in our case , the latter may have been the stronger factor .
vasodilation resulting from the stimulation of the dorsal root , which is thought to be a separate entity from sympathetic nervous system , has been discovered .
this arises from spinal gray matters , and the preganglionic fibers passes the dorsal root and dorsal root ganglions , changing postganglionic fiber and ultimately , peripheral ganglions and skin temperature21 ) .
furthermore , parasympathetic nerves are also involved in regulation of skin temperature , which may be a clue explaining the rise in temperature at fibular area and cutaneous blood flow following sensory change with compression test .
interestingly the temperatures at dorsal foot area do not show any significant changes and were elevated more than fibular area . the study performed by zhang et al.21 )
presents thermal data of the upper body measured indoor at 23. in this case , the mean temperatures of upper body sectors are distributed from 29 to 32. this study demonstrates lower extremity temperature of our case , being maintained at 31.08 to 31.83 regardless of compression . in other words ,
our case of ir thermography data follows the temperature distribution pattern obtained at 23 indoor . the magnitude temperature of difference between left and right side of the same anatomic location was 0.1 , 0.2 , 0.3 , and 0.4 regardless of indoor temperature ( 20 or 23 ) , in both 1995 and 1999 study21 ) .
the elevated temperature of the foot dorsum compared to the fibula before the surgery ( table 1 ) may be attributed to tumor effect .
the situation where the temperature of dorsum was 0.58 higher instead of 0.3 was determined as abnormal6 ) .
this is also well demonstrated in uematsu , where carpal tunnel syndrome was correlated with electromyography ( emg)18 ) .
the degree of median nerve lesion was classified as mild , moderate , or severe according to emg findings , and mild and moderate compression group demonstrated thermal elevation while in severe compression group , both thermal elevation and depression was observed . in other words ,
palmar temperature rises as the severity of median nerve compression increases and then drops as thenar muscle atrophy develops as the result of chronic severe carpal tunnel syndrome . since peripheral nerves include sympathetic nerves involved in vasoconstriction of the anatomic area , the tumor located at sensory branch of the deep peroneal nerve may have suppressed the vasoconstriction of the surround area , resulting in vasodilation and the following hyperthermia of the right dorsum and toe compared to the left side . there are numerous other factors influencing skin temperature , including emotional stress and depression , which can affect autonomic dysfunction4 ) , as well as the circadian rhythm , which results in diurnal variation of body temperature7 ) .
it shows temperature change according to autonomic nervous system tone or change in circulation caused by various etiologies . therefore , although it shows temperature changes , it does not clarify what the nature of the causative lesion is .
considering these variables , future studies and analyses controlling for these factors may be needed .
when the mass , pnst , was compressed , there is a ir thermographic - thermal elevation at pnst proximal part with subjective pain .
mass excision relieves the patient 's symptom , and there is no definite thermal change at post - operative ir thermograpy .
however , tumors that occurred in peroneal nerve have a similar symptoms with hld , or symptoms caused by nerve irritation or compression .
although , ir thermographic findings are not specific , as discussed previously , there are differences in ir thermography , and it is useful and supportive in our case . therefore , there are possible usefulness of ir thermography in evaluating symptoms caused by nerve irritation or compression , and possible limitation from various etiologies .
further study will be needed to clarify which range of temperature change can be interpreted as significant result and to get specific result without numerous other factors influencing skin temperature .
 we report a case of neurilemmoma of deep peroneal nerve sensory branch that triggered sensory change with compression test on lower extremity . 
 after resection of tumor , there are evoked thermal changes on pre- and post - operative infrared ( ir ) thermographic images . a 52-year - old female presented with low back pain , sciatica , and sensory change on the dorsal side of the right foot and big toe that has lasted for 9 months . 
 she also presented with right tibial mass sized 1.2 cm by 1.4 cm . 
 ultrasonographic imaging revealed a peripheral nerve sheath tumor arising from the peroneal nerve . 
 ir thermographic image showed hyperthermia when the neurilemoma induced sensory change with compression test on the fibular area , dorsum of foot , and big toe . 
 after surgery , the symptoms and thermographic changes were relieved and disappeared . 
 the clinical , surgical , radiographic , and thermographic perspectives regarding this case are discussed . 
INTRODUCTION
CASE REPORT
DISCUSSION
CONCLUSION