In Reply:—
Dr. Aldrete wonders how the fusiform anterior epidural mass got there. We postulate that shortly after the first epidural steroid injection, a granulomatous response occurred with thickening of the dura; after the second block, the patient was becoming more symptomatic because of the increasing size of the mass. Superiorly, the inflammation from the mass extended through the foramen magnum, accounting for the postural component of the headaches, so-called axial loading. Inferiorly, the anatomy became distorted from the swelling and mass effect, predisposing to the “lightning bolt” paraesthesia and dural puncture during the third block. The procedure was not aborted, allowing triamcinolone and its preservative to gain access into the subarachnoid space with resultant arachnoiditis. The dural tear did not leak substantial amounts of cerebrospinal fluid until the overall swelling and mass effect of the granuloma lessened many months later. This led to “secondary” intracranial hypotension, which accounted for the incapacitating postural headaches. We suspect that the mass was caused by the preservative in the triamcinolone acetonide (Kenalog; Bristol-Myers Squibb, Princeton, NJ) and not the steroid itself, but there is no way of knowing. The only way to know what the mass was composed of would be to obtain a biopsy, which would involve opening up the dura. This was not performed during surgery because of the risks involved. Injection of triamcinolone acetonide should have been aborted during the third cervical epidural steroid injection (CESI) block in our patient because of suspicion of wet tap due to the paresthesia with radicular irritation.
As far as the technical aspects of CESI, there is no clear consensus as to the superiority of one approach over another (e.g. , prone vs. sitting, use of fluoroscopy, transforaminal vs. interlaminar). In academic practices, the most common position used for CESI was prone (46%), followed by sitting (35%) and lateral decubitus (10%).1Only 39% of academic institutions reported use of fluoroscopy for CESI.1At our institution, the transforaminal approach is preferred (Mohan Kareti, M.D., Assistant Professor, Director of Pain Management, Department of Anesthesia, MetroHealth Medical Center, Case Western Reserve University, Cleveland, Ohio, verbal communication, May 2004). This approach can be used at nearly any level. The position for transforaminal injection is supine, with fluoroscopy on anterior-posterior and lateral views to confirm proper needle position. Aspiration is performed, and dye is injected to confirm epidural flow and to rule out intravascular (intraarterial), intrathecal, or soft tissue infiltration. For the interlaminar approach, injections are performed below C7, with the patient in the prone position.
The current patient’s blocks were performed at an outside hospital, with the patient in the sitting position without head support, using a hanging drop method and intermittent fluoroscopy. Dr. Mchaourab reminds us that there is virtually no cervical posterior epidural space above C7.2,3Perhaps this unfortunate complication might have been avoided had the epidural been performed at a lower level. As mentioned by Dr. Aldrete, there is no solid evidence that depositing the steroid medication precisely at the level where pathologic findings have been reported produces better results than if injected one or two spaces away.
Although the patient did have low-lying cerebellar tonsils 7 months after CESI as part of her constellation of symptoms and signs of intracranial hypotension, she did not have a Chiari I malformation as suggested by Dr. Aldrete at the time of the initial CESIs. “Sinking” or “sagging” of the brain is a common finding in patients with intracranial hypotension and may mimic type I Chiari malformation.4
Fibrin glue, a mixture of fibrinogen, factor XIII, fibronectin, aprotinin, plasminogen, thrombin, and calcium, has a high tensile strength, tolerates moist environments, and forms a temporary biologic dural seal until healing occurs.5Fibrin glue is widely used in neurosurgery and otology to achieve watertight dural closure.6Regarding the long-term safety of fibrin glue, the patient is doing fine 17 months after surgery, the mass has regressed, the symptoms of intracranial hypotension have resolved, and the patient has returned to her former position as an attending anesthesiologist.
* MetroHealth Medical Center, Case Western Reserve University, Cleveland, Ohio. csmith@metrohealth.org
