metronidazole is a commonly used antimicrobial agent used for the treatment of protozoal and bacterial infection . this drug is in its inactive state when administered to a patient , allowing selective targeting . once in the system the drug is taken up by the target and metabolized into its active form , inhibiting its normal function . the most common side effects of metronidazole include nausea , headaches and the metallic taste in the mouth . in some cases , high doses and/or prolong use may produce several neurologic side effects including peripheral neuropathy , cerebellopathy , encephalopathy and seizure2,3,5,7 ) . recently , we encountered a case of metronidazole - induced encephalopathy ( mie ) with peripheral polyneuropathy ( ppn ) in patient with spinal cord injury ( sci ) . mie with ppn is a very rare occurrence let alone a mie on a patient with spinal cord injury , which has not been previously documented . whether the encephalopathy and ppn was induced by metronidazole or some other factor in patient with spinal cord injury , diagnosis at first glance proved to be very difficult . this was because the sure signs ( ataxia , gait difficulty , tingling sensation in lower extremity and so on ) of the drug 's side effects were not present due to the paraplegia . however , observing this patient carefully , we have noticed something that might serve as detection for mie with ppn despite paraplegia . a 32-year - old woman injured in a skiing accident a month before her visit , was transferred to our institute from another hospital as a result of her paraplegia . initial workshop at the other hospital showed bursting fractures of t6 , t7 , t8 vertebral bodies , hemothorax and multiple rib fractures ( fig . 1 ) . neurologic examination revealed a motor and sensory impairment of grade a at the t6 level , according to the american spinal injury association ( asia ) scale . she was examined for vaginal discharge at the previous hospital and was diagnosed with erosion and acute inflammation of the cervix . she was then treated with 2 g of metronidazole daily for fifty days because of the vaginal discharge . one month after the first administration of metronidazole , she complained of a mild tingling sensation on both forearms and all fingers as stocking glove type . however laboratory findings from blood and urine samples did not show any specific abnormalities ( hb : 12.4 g / dl , protein : 5.7 gm / dl , albumin : 3.5 g / dl , got : 38 iu / l , gpt : 59 iu / l , na : 142meq / l , k : 4.3meq / l , ca : 9.4mg / dl , p : 4.9mg / dl ) . we examined tinnel and phalen sign and proceeded to do an electrophysiological study in the upper extremities as well as a cervical spine mri , checking for carpal tunnel syndrome ( cts ) , syringomyelia , and other complications that might have risen in the patient with spinal cord injury . forty five days after the first treatment of metronidazole she developed mild nausea and vomiting with dizziness . we performed esophagogastroduodenoscopy to check for gastric ulcer , but observed only atrophic gastritis on a pyloric antrum . fifty days after the first medication of metronidazole , we observed dysarthria and weakness of both hands . laboratory findings from blood showed no abnormalities ( hb : 12.9 g / dl , wbc count : 7,200 ul esr : 14mm / hr , protein : 5.8 gm / dl , albumin : 3.8 g / dl , got : 22 iu / l , gpt : 18 iu / l , na : 138meq / l , k : 3.9meq / l , ca : 9.1mg / dl , p : 4.7mg / dl , vit . b12 : 611 pg / ml[200 - 950 ] , folate : 4.34 ng / ml[3 - 17 ] ) . the brain magnetic resonanace image ( mri ) with diffusion - weighted image ( dwi ) was performed to rule out brain lesions . we also performed electrophysiologc examinations of upper and lower limbs to find signs of peripheral polyneuropathy , simultaneously . we observed high intensities of superior olivary nuclei , dentate nuclei of cerebellum and splenium of corpus callosum on mri ( figs . 2 and 3 ) . in addition , the findings of electrophysiological examination revealed that amplitudes ( base to peak amplitude ) were below normal or absent on sensory nerves of more than 3 limbs , on the other hand , onset latency and velocity of those were normal findings . also latency , amplitude and conduction velocity of motor nerves were normal , but , conduction velocity of peroneal and tibial nerve were lower limit normal . because of above results , we considered ppn as axonal loss sensory type in this case ( table 1 and 2 ) . before we could suspect that metronidazole was behind the new symptoms , we first had to rule out wernicke encephalopathy ( we ) because of brain mri images . mie and we have similar histologic findings6 ; therefore it was necessary to differentiate the two . we have a triad of symptoms including confusion , ophthalmoplegia and gait ataxia while mie has dysarthria and gait ataxia . we examined the level of thiamine hydrochloride because its deficiency could result in we . showing no lack of thiamine hydrochloride , we correlated the mr imaging with the clinical symptoms and diagnosed her as having mie with ppn and stopped the medication of metronidazole . two days later , dysarthria and nausea improved slowly but a little tingling sensation and weakness of both hands persisted for more than three months . three month later , we rechecked the electrophysiological condition in the upper and lower extremity , and it did not revealed - some recovery . neurotoxicity is one of the more serious adverse effects of metronidazole therapy , but it is very rare . the types of neurological side effects ranges from frequent reports of reversible cerebellopathy and peripheral neuropathy , to other uncommon , but documented , neurotoxicities such as encephalopathy , seizure and mental confusion . ahmed et al . described the imaging findings of metronidazole toxicity in 1995 in a 45-year - old woman who developed nausea , vomiting , dysarthria and confusion after consuming 35 g of metronidazole over a 30-day course of therapy1 ) . horlen et al . reported imaging findings of presumed metronidazole toxicity in a 35-year - old male patient with liver cirrhosis who had consumed greater than 60 g metronidazole over a 55-day period and developed clinical symptoms consistent with metronidazole toxicity in 20005 ) . heaney et al . reported imaging findings of a 74-year - old male patient with progressive bilateral lower extremity weakness and dysarthria in 20034 ) . the patient had consumed a total of more than 75 g metronidazole over 8-weeks period . in each of these cases , including ours , there was a symmetrically abnormal intensity in the deep cerebella nuclei in the t2-weighted image or dwi . these cases all demonstrated changes within the deep cerebella nuclei . therefore this area is likely to be the most sensitive to the effects of metronidazole toxicity and also the most observable manifestation of metronidazole toxicity . however , only our case showed bilateral symmetric hyperintense lesions in the superior olivary nuclei of the dorsal pons on the mr imaging of the brain . in each of the cases , including ours , the symptoms rapidly improved following cessation of metronidazole therapy . mie may produce symptoms of progressive gait disturbance , ataxia and dysarthria , and toxic peripheral neuropathy does symptoms of sensory ataxia , tingling sensation and paresthesia . unfortunately , our patient showed only dysarthria and a tingling sensation of hands because of her paraplegia due to her spinal cord injury . another obstacle was that paraplegia left her with dull sensation to her lower extremities , which meant that the tingling would not have been noticed there correctly . however , we did n't doubt that symptom caused by peripheral polyneuro pathy , because that was uncommon in patient with spinal cord injury . and , because we could not examine ataxia and gait disturbance , we did not know mie . also , ncs study and brain mri mie is a reversible disease which can improve a few weeks after discontinuation of metronidazole1,5,6 ) . therefore , correct and early diagnosis is very important to treat patients with mie . but considering the rare situation the patient was in , mie or other neurological problems may be difficult to diagnose , especially when such side effects are not common . the importance of an active differential diagnosis can be seen in our case . whether the initial tingling of the hands may have been a sign of early mie or other neurological problem , it would be the best to consider all possible causes before the onset of new symptoms , especially when the severity of the disease is measured by the time of detection . in special circumstances such as a paraplegia patient , these symptoms may not be present . however , if a tingling sensation in the hands or one of cerebellar symptoms such as dysarthria , dysmetria , and so on , is observed in patient with spinal cord injury , it is important to consider and to evaluate a possibility of peripheral polyneuropathy , or encephalopathy especially , patient take some metronidazole , because an early detection means a better recovery .
metronidazole may produce a number of neurologic side effects including peripheral neuropathy , seizure , encephalopathy . 
 we experienced neurological side effects of metronidazole . 
 the 32-year - old female patient with spinal cord injury was diagnosed as encephalophathy and peripheral polyneuropathy resulting from complication of metronidazole . 
 it was difficult to diagnose at first glance using clinical findings because of paraplegia due to spinal cord injury . 
 but through magnetic resonance imaging with diffusion weighted imaging and electrophysiologic study , the patient showed to have characteristic abnormalities that of a person suffering from metronidazole - induced encephalopathy and peripheral polyneuropathy . 
 whether the symptoms were caused by a peripheral nerve lesion or mie , the patient 's paraplegia prevented to appear other symptoms , such as ataxic gait and seizure , from manifesting . 
 in such case as this , an active differentiated diagnosis is crucial .