a 56-year - old female patient presented with neck and left shoulder pain radiating to the left upper extremity . however , no objective loss of sensory or motor function was observed . although conservative treatments , including as resting , traction , non - steroidal anti - inflammatory drug and muscle relaxant were properly done for two weeks , her pain was not improved . the neurosurgeon requested a selective left c6 nerve root block . a cervical spine plain film radiograph showed degenerative cervical spondylosis ( fig . the radiologist reported that the cervical magnetic resonance image ( mri ) revealed a left - sided foraminal stenosis at the c5 - 6 level . before performing the procedure , the author re - examined the mri meticulously . although the radiologist did not mention the va , the author detected a tortuous anatomical variation in the va at the left c5 - 6 level on the mri ( fig . the author ordered a ct angiogram to show the anatomical variations in the va more precisely . in particular , the 3d reconstruction image showed a unilateral atypical entrance into the foramen transversarium ( ft ) of the fifth cervical vertebra and a hypoplastic abnormality of the right va ( fig . the diameters of the left and right va were 4.86 mm and 2.47 mm at the lower endplate level of c5 , respectively . the diameter of the left va was 2.39 mm greater than that of the right at the c5 lower endplate . the maximum diameters of the tortuous component of the left and right va were 9.80 mm and 6.64 mm , respectively . the maximum diameter of the tortuous component of the left va was 3.16 mm greater than that of the right . the left va entered the ft of the sixth cervical vertebra , whereas right entered the fifth . to minimize adverse events , the procedure was performed with dexamethasone ( non - particulated steroid ) and under ct guidance . the patient was placed in the supine position on a ct table with her head tilted slightly to the right . before scanning , a wire was placed on the lateral side of her neck to use as a marker . the patient was scanned to identify a suitable approach point for the 23 g spinal needle . a path that avoided contact with the periosteum and deep cervical plexus was chosen to minimize patient discomfort . the scanning level for the ct fluoroscopy ( ctf ) image was selected and the target lesion was scanned to a thickness of 1 mm from the middle of the c5 body to the middle of the c6 body . the skin entry point and target point for the spinal needle was determined on the ct scan view ( fig . 3a ) and marked on the neck . before the cste was performed , 2% lidocaine was aseptically infiltrated into the skin and subcutaneous tissue . the needle was advanced slowly into the left c5 - 6 foraminal area while avoiding the large tortuous va . it was confirmed that the 23 g spinal needle was located exactly within the left - sided c5 - 6 foraminal area using 0.3 ml of radio - contrast dye ( fig . pain was relieved immediately after completion of the procedure and two weeks later , vas score was decreased to 1 or 0 of 10 . the patient 's symptoms were relieved almost completely and did not recur in the following 3 months . cste is the injection of local anesthetics and anti - inflammatory steroids into the peri - radicular space ( the epidural space surrounding the spinal cord and the nerve root ) using a transforaminal approach . despite the safety of this procedure , cste carries an inherent risk of serious complications or even death . in many cases , these complications occur due to direct va injury or unintentional injection into the va [ 4 - 7 ] . however , some of the complications can be minimized or avoided by promoting awareness of the anatomy or their severity can be reduced by modifying the procedure . proposed a radiographic grading system for va tortuosity on anteroposterior cervical spine plain film radiographs and angiograms . they defined the following four types : type 1 , the va is straight and in zone i ( outside of the lateral end of the luschka joint ) ; type 2 , the artery is mildly tortuous and in zone i ; type 3 , the artery has a loop formation , and the most medial portion is in zone ii ( between the lateral and medial end of the luschka joint ) ; and type 4 , the artery has a loop formation and migration is in zone iii ( medial to the luschka joint ) . in addition , they graded the spondylotic change from a lateral view of the cervical spine radiography as follows : grade 1 , no spondylotic change , disc height is normal ; grade 2 , disc height is low but > 50% of normal height , and the change is observed in only one level ; grade 3 , disc height is low at more than two levels or severe narrowing of the disc space < 50% of normal disc height . they suggested that va loop formation is associated with cervical spondylotic changes . in the present case , ct angiogram showed a large left va with a type 3 tortuous anatomical variation according to the grading system of oga et al . the spondylotic changes on the cervical spine plain radiographs were grade 2 according to the grading system of oga et al . iatrogenic direct va injuries may be caused by various diagnostic or therapeutic procedures , including diagnostic cerebral angiograms , central venous catheterization , chiropractic manipulation , percutaneous nerve or sympathetic chain block such as a stellate ganglion block ( sgb ) . inamasu and guiot   summarized 16 cases of va - related complications that occurred during percutaneous nerve block procedures . most of the reported adverse events resulted not from direct va injury , but unintentional injection into the va of local anesthetics or steroids . only 2 cases of a total 16 cases were the result of direct va injuries . one was airway obstruction due to laceration and hemorrhage , and the other was brainstem infarction followed by altered mental status due to dissection and thrombosis of va . the other 14 cases were resulted from injection of local anesthetics or steroids into the va , which caused reversible grand - mal seizures or transient locked - in syndromes after injection of local anesthetics such as lidocaine or bupivacaine , and a fatal embolic brainstem infarction after particulated steroid injection during cste . according to dreyfuss et al . , the difference in efficacy between non - particulated ( dexamethasone ) and particulated steroids ( triamcinolone ) , was neither statistically nor clinically significant . they suggested that a theoretically safer non - particulated steroids could be a valid alternative to particulated steroids . half of them occurred during sgbs and just only two cases during cervical nerve root blocks . although a fatal va dissection after a transforaminal c7 nerve root block has been reported , it is rare for the arterial puncture itself to cause a major va injury , because a small - caliber spinal needle is generally used for cste to minimize trauma . however , if this did occur , the consequences could be grave . in addition , anatomical variations in the va can cause disastrous complications and can greatly enhance the occurrence of such complications during various diagnostic or therapeutic procedures . therefore , for that reason , cste under ct guidance is recommended and was performed in the present case . although , unlike fluoroscopy guidance , ct guidance may takes longer time , exposes the patient to greater amounts of radiation , and prohibits the dynamic injection of contrast material , it has the advantage of better anatomic resolution and enables direct visualization of the va . structures supplied by the va include the occipital lobe of the cerebrum , the cerebellum , the brain stem , and the upper spinal cord . in the ct angiogram of the present case , specifically , the diameters of the right va were 2.47 mm and 2.33 mm at the lower and upper endplate levels of c5 and c6 , respectively . in a retrospective review , eskander et al . classified va anomalies into the following three main groups : intraforaminal , extraforaminal and arterial anomalies . they reported that intraforaminal anomaly refers to midline migration of the va , which was due to degeneration or trauma in 7.6% ( 19/250 ) of patients . in the cases of extraforaminal anomaly , only 92% ( 460/500 ) of vas entered the ft at the c6 level . in the cases of arterial anomaly , there are also reports of fenestrated , duplicated , and hypoplastic arteries . in eskander 's review , hypoplastic vas were verified in 10% ( 25/250 ) of the patients . however , the exact definition and clinical significance of va hypoplasia has not been established . chen et al .   found that a 2.5 mm va diameter is ideal for discriminating marked flow asymmetry and low va flow volume , and proposed a va diameter  2.5 mm to be an ideal definition of va hypoplasia . it is clear that the present case had hypoplasia of the right va because the diameter of the right va was less than 2.5 mm . va hypoplasia has been generally regarded as a normal variant because the contralateral va commonly has an increased compensatory flow . however , some authors have recently proposed that va hypoplasia can be a predisposing factor for posterior circulation stroke . patients with tortuous va should understand that the risk of posterior brain infarct is high and we , as health professionals , must explain this to them thoroughly . practitioners are wary of injuring the va during cste . moreover , if unilateral va hypoplasia is present , as in the present case , injury to the dominant va may cause lethal complications as a result of insufficient blood flow to the brain stem . in addition , eskander et al .   reported a spiraling effect that was identified in all patients with migrating vas . as the va moves from caudal to cephalad , the va migrates medially with a clockwise rotation . if interventional treatment ( surgery or injections ) is planned , this should be considered as very important . and , if this spiraling has a large effect on the nerve root , it may be one of the components of the original pathology . in the present case , radicular pain was thought to be due , not to osteophyte or disc herniation , but to the mass effect of the tortuous va on the nerve root . sometimes , as in the present case , we have found that radiologists do not comment on va asymmetry when present . if we have any doubts about a radiologist 's report , we should examine the scans repeatedly before performing cste , to identify whether or not the va has any anatomical variations . this is the first report that cste was performed for tortuous anatomical variation of va under ct guidance . it is important to carefully identify whether any anatomical variations in va exist before performing procedures , such as cste , that can cause vertebral arterial injury , and ensure that needle placement is correct during the procedure and that appropriate drugs , such as non - particulated steroids , are selected . we also recommend that ct guidance ( possibly ct fluoroscopy ) is used for cste if possible , given its significantly greater safety in comparison with fluoroscopy .
a 56-year - old woman complained of radiating pain to the left arm . 
 she was diagnosed with left - sided foraminal stenosis at the c5 - 6 level . 
 the neurosurgeon requested a left c6 cervical selective transforaminal epidural block ( cste ) . 
 cervical mri showed a left - sided large tortuous vertebral artery ( va ) at the c5 - 6 level . before performing cste , 
 a ct angiogram was carried out and showed bilateral tortuous vas . to minimize adverse events , 
 cste was performed with non - particulated steroids and under ct guidance . following the procedure , 
 the patient 's symptoms were relieved completely . 
 although complication rates of cste are generally low , if it occurs , disastrous situation could be . 
 additionally , if the patient has anatomical variations , the possibility of a complication occurring is greatly increased . 
 it is therefore important to determine whether the patient has any anatomical variations of the va before performing procedures such as cste , and to ensure that needle placement is correct during the procedure and an appropriate drug , such as a non - particulated steroid , is selected .