I am trying to upload some slides from a M&M conference I did regarding subdural injections. I personally have seen at least 5 of these in the last year, mostly with the placement of indwelling tunnelled epidural catheters that have migrated into the subdural space. However these can happen during routine interlaminar epidural injections.
Unfortunately, someone stole my USB stick, so the pictures and the references were lost. What you see is called 'railroad tracks'. It is the contrast outlining the lateral boarders of the epidural space in a very thin manner. A very small amount of injectate can travel quite a distance, as evidences in my M&M case.
Patchy blocks can be caused by a number of things. Those that perform epidurals with contrast know that the epidural plica mediana dorsalis will often contain the contrast to one side (which is another argument for bilatereal transforaminal injections vs. interlaminar).
During my anesthesia training it seemed that anytime anyone performed a spinal that did not work or was patchy they blamed it on a subdural injection. Although possible, I do not believe this to be the case.
Couldn't upload a Power point so I just cut and paste the 6 slides here.
Subdural space:
48-year-old white female, a U.S. Government employee/protocol specialist for the U.S. Marines who is getting ready to retire. She presently lives in Naples, Italy and is here for a second opinion at her own request. Basically, she has undergone an ORIF of her right distal fibular nonunion in June of 2005 in Naples, Italy. At that time, she had iliac crest bone graft and a single screw placed in the distal fibula. Since then, she has subsequently developed CRPS and is under treatment for this, but is here now for an addition opinion to see if everything is coming along as expected or if anything else needs to or should be done. She initially broke her ankle in February of 2005 when she was walking down a gravel road and stepped into a pothole and twisted her ankle. She was in a cast for approximately 8 weeks, nonweightbearing, but did develop the nonunion. When she was taken out of the cast for the surgery, she was 50% weightbearing initially. Before the surgery, she was walking up and down some stairs and this aggravated the nonunion, requiring the surgical intervention. She has undergone 3 sympathetic nerve blocks, all of which have helped her somewhat, and she is presently on Neurontin which is helping as well.
Unremarkable TEC(tunnelled epidural catheter) placed on 10/03/05.
Uneventful hospitalization 10/03-10/06 except for having severe back pain at catheter site treated with fentanyl. d/c on Fentanyl 2 mcg/ML and Bupivicaine .0625% 300 ML at basal rate of 4 ML per hour and demand dose of 2 ML interval of 20 minutes
10/07 Friday
7am called service- numb right foot when she got up.
She was told to hold her infusion for and hour and try to walk around.
8am she restarted infusion 2:30pm Numbness has progressed up her leg to her hip and back, and says now her left arm is numb to her shoulder
she states she is having difficulty breathing, and that she feels like she is breathing underwater.
3:00 pm pump off
4:45 gets to clinic. States she is still having entire left sided numbness from the top of her neck to her toes. Also now her right hand and arm are feeling numb as well. Breathing difficulty persists
Physical Exam (Yes, we did one)
BP 140/82, Pulse 76, O2 sat 100%, RR 22 general: NAD, awake, alert oriented. lungs: clear b/l no crackles or wheezing heart: s1s2 RRR UE- strength wnl reflexes 2+ sensory Left UE WNL, RUE pinprick normal, loss of temperature differentiation to the shoulder/base of neck LE-strength wnl sensory Left LE WNL, RLE pinprick normal, loss of temperature differentiation reflexes 2+
Epidurogram:
Epidural Catheter Dye Injection: The epidural catheter was removed in sterile fashion. Thecatheter tip was scubbed with betadyne and the placed on a sterile drape. Omnipaque 300 dye was injected under flouroscopy and initially the dye spread in an epidural fashion about the L4/5 nerve roots on the right side, as was seen with initial placement. As more dye was injected (7cc) it was noticed that there was spread along the right side of what looked to possibly be the subdural space to at least the level of T4. At this point the decision was made to remove the epidural catheter. The bandages were removed and the catheter was removed tip intact. Betadyne was then placed over the incision sites and the wounds were bandaged accordingly. Assessment: Subdural migration of Epidural catheter removed tip intact
Subdural space:
a potential cavity between the dura and arachnoid mater, containing a small volume of serous fluid Grays
The space runs up from the lower border of the second sacral vertebra into the cranial cavity as high as the diaphragma sellae in the floor of the third ventricle (2) but does not communicate with the subarachnoid space. It is continued onto the cranial and spinal nerves for a short distance. The space appears to be widest in the cervical region
Jones MD, Newton TH. Inadvertent extra-arachnoid injections in myelography. Radiology 1963 80:818-821.
The dura is composed of elongated, flattened fibroblasts and copious amounts of extracellular collagen. A specialized layer of fibroblasts, the dural border cell layer, is found at the dura-arachnoid junction and is characterized by flattened fibroblasts, no extracellular collagen, extracellular spaces, and few cell junctions. These features combine to create a layer of the inner dura that is structurally weak when compared with external portions of the dura and the internally located arachnoid
Haines DE. On the question of a subdural space. The Anatomical Record 1991 230:3-21.
