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myoclonus is a brief , involuntary twitching of a muscle or a group of muscles .
it has been classified into cortical , subcortical , spinal , and peripheral lesions12 ) .
although many diseases have been reported as a cause of myoclonus8 ) , only one recently reported a case of spinal myoclonus has been attributed to cervical herniated intervertebral disc ( hivd ) .
although spinal myoclonus can be difficult to manage , some drugs such as clonazepam and tetrabenazine hydrochloride may be effective5,8 ) .
many authors have tried to treat myoclonus with spinal or epidural blocks in difficult cases , which would not infrequently cause worse results .
we report a case of propriospinal myoclonus ( psm ) that might be induced by lumbar hivd in a 15-year - old female who has been successfully treated with an epidural steroid injection using a transforaminal approach .
she was suspected to have left lumbar hivd at l5-s1 based on a physical examination , however , her pain was aggravated in spite of conservative management for 3 days .
she also experienced a brief involuntary muscle twitching involving the left lower leg and trunk . a whole spine magnetic resonance imaging ( mri )
routine laboratory , hematologic studies , electrolyte study included calcium , magnesium , copper and ceruloplasmin concentration and cerebrospinal fluid study were unremarkable .
the nerve conduction test showed that the f - wave latency was prolonged and the h - reflex was normal in the left peroneal nerve , which is not a peripheral neuropathic finding .
however , intermittent brief synchronous activity was noted in the left sternocleidomastoid , rectus abdominalis , gluteus medius , and gastrocnemius muscles based on surface electro - myography , which was consistent with psm .
the myoclonus was characterized by the hip and knee joints extending 1 - 2 times per second with the lower back extended .
myoclonus was decreased to 1 - 2 times per 3 - 4 seconds in frequency after administration of clonazepam ( 0.5 mg ) , but there was no further improvement in symptoms . on physical examination , myoclonus and pain were aggravated in the straight leg raising test at approximately 50 degrees hip flexion or ankle dorsiflexion .
myoclonus was intensified during the one - leg standing and spread to the thoracic muscles .
a transforaminal epidural steroid injection was delivered with triamcinolone ( 20 mg ) and 0.3% lidocaine to the left l5 , s1 root on one occasion ( fig .
, the sciatic pain was disappeared immediately and the myoclonus was decreased to 1 - 2 times per 10 seconds in frequency .
we observed her without medication in the outpatient clinic for 6 months after the procedure .
brown and colleagues2 ) recommended that spinal myoclonus would be classified as segmental spinal myoclonus and psm in 1991 .
the affected area may include direct damage of the spinal cord or may cause abnormal changes in the function of the spinal cord .
but psm involves the following : all of the spinal cord , rather than a specific segment , complex muscles jerks ; more extensive simultaneous involvement of muscles , such as the trunk and limbs ; the pattern is usually arrhythmic ; and stimulus - sensitive with a delay due to the slow conducting propriospinal nerve fibers .
according to a psm study , diagnostic clues for psm include widespread rhythmic or arrhythmic myoclonus prominently involving the trunk muscles and sparing the cranially - innervated muscles5 ) . in our case , the myoclonic jerks were arrhythmic , starting from the left leg and extending to the trunk , ascending , and aggravated with nerve stimulation ( e.g. , straight leg raising and one - leg standing ) . furthermore , there are no myoclonic jerks in the cranial - innervated muscles .
spinal myoclonus has been associated with laminectomies , the remote effects of cancer , spinal cord injuries , post - operative pseudomeningoceles , laparotomies , thoracic sympathectomies , poliomyelitis , herpes myelitis , lumbosacral radiculopathies , spinal epidural blocks , myelopathy due to demyelination , electrical injuries , acquired immunodeficiency syndrome , multiple sclerosis and cervical spondylosis8,9 ) . in rare occasions
although various causes have been reported1,6,11,14,15 ) , there has been only one report of a cervical disc as the cause of psm resulting from disc disease .
capelle , et al.,4 ) described a patient who presented with right c6 radiculopathy due to hivd c5 - 6 and myoclonic twitches predominantly affecting the abdominal muscles but spreading to adjacent muscles which was treated with discectomy and cage augmented fusion . to the date , this report might be the first report of psm with lumbar disc disease .
a variety of mechanisms have been proposed for spinal myoclonus , including dysfunction of segmental spinal cord circuitry , deficient inhibitory glycinergic transmission in the spinal cord , subsequent release of synchronous motor neuron oscillations within segments of the cord , and vitamin b12 deficiency causing vacuolar swelling of the myelin layers in the mid - thoracic cord and resulting in degeneration of the descending pyramidal and ascending posterior column traces18 ) .
also , according to campos , et al.,3 ) there is evidence that various possible mechanisms can be involved : loss of inhibitory function of local dorsal horn interneurons , abnormal hyperactivity of local anterior horn neurons , aberrant local axons re - excitations , and loss of inhibition from supra - segmental descending pathways .
ogata , et al.,16 ) experienced that psm due to injury to the l4 nerve root during epidural anesthesia was treated by l4 root block using 1.5ml of 1% lidocaine .
he described that an injury to the left l4 nerve root possibly cause an abnormal transmission of the impulses or ectopic hyperexcitability in the nerve root , which might lead to the disturbance of the spinal inhibitory interneurons and hyperexcitability of the anterior horn cells causing myoclonus .
the authors assumed that local anesthetic agents which was administered to the spinal epidural space via a caudal or interlaminar injection may distribute more in the posterior lateral part than in the anterior part of spinal canal , in which the effect of the local anesthetic drug on inhibitory neurons might have led to a loss of inhibitory function in the spinal cord7,13 ) .
thus , a transforaminal injection has an advantage over a caudal or trans - interlamina block . in the transforaminal injection ,
the injected drugs spread more onto the ventral surface of the spinal cord and can block the lesional root at the same time ( fig .
symptoms of myoclonus have been subsided by avoiding the disturbance of the spinal inhibitory interneurons activity .
this case shows that hivd may be the one of the causes of myoclonus , and transforaminal epidural injection can be option of treatments , in which can approach the ventral surface of the spinal cord and affected root in order to avoid the disturbance of the spinal inhibitory interneurons activity .
we recommend epidural steroid injections via the transforaminal approach as a treatment option for psm .
the cause of propriospinal myoclonus ( psm ) is idiopathic . 
 cervical trauma , ischemic myelopathy secondary to a spinal dural arteriovenous fistula , syringomyelia , lyme neuroborreliosis , human immunodeficiency virus central nervous system infection , and cervical disc herniation can be the cause of psm , but lumbar herniated intervertebral disc ( hivd ) induced psm has not been reported . 
 we describe a patient who presented with psm induced by hivd and was treated with an epidural steroid injection using a transforaminal approach .