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 .