DIAGRAMMATIC ANALYSIS OF SUBARACHNOID CONTRAST SPREAD IN THE CONTRALATERAL OBLIQUE VIEW: A TECHNICAL REPORT

Interlaminar epidural steroid injections are commonly used in clinical practice for the relief of low back pain. Reliable deposition of medication in the epidural space is important in producing significant results. Pathological conditions, including vertebral osteoarthritis, degenerative disc disease, and spinal stenosis, are frequently treated with epidural steroid injections. Associated degenerative features such as ligamentum flavum hypertrophy, facet joint hypertrophy, and osteophyte formation can lead to significant alterations in the anatomy of the epidural space. Epidurograms, prior to steroid injection, aid the physician in identifying the epidural space, as a false loss of resistance can occur. Extradural, subdural, intradural, and subarachnoid contrast spread has been demonstrated in the anteroposterior and lateral views; but, has not previously been demonstrated in the contralateral oblique (CLO) view. This technical report is the first to demonstrate concomitant epidural and subarachnoid spread in the contralateral oblique view after inadvertent low volume subarachnoid injection, as might happen in clinical practice. In this technical report, we demonstrate both epidural and subarachnoid contrast spread in the contralateral oblique view and compare it to the anteroposterior view. In an oblique view, epidural contrast spread is observed to approximate the ventral margin of the superior aspect of the lamina while subarachnoid contrast spread has a distinct demarcation at the ventral laminar margin. In an anteroposterior view, epidural spread is confirmed by spread of the dye along the nerve roots and beyond the margins of the pedicles. The CLO view provides an accurate and consistent visualization of the epidural space; irrespective of the obliquity, epidural contrast is observed to approximate the ventral margin of the superior aspect of the lamina. In the CLO view, if contrast spread does not approximate the lamina, then intrathecal injection must be considered. Key words: Epidural steroid injection, epidurogram, epidural spread, subarachnoid injection, intrathecal spread, fluoroscopy, contralateral oblique view

Subarachnoid injection of ifenprodil and ketamine association improves the anti-hyperalgesic action of ketamine in dogs

To test clinically whether a small dose of ifenprodil can enhance the anti-hyperalgesic effect of ketamine in dogs, a prospective randomized cross-over study was done with eight mongrel dogs (weighing 16.9 ± 3.7kg). Animals received two distinct treatments: ketamine (0.3mg kg-1; KT) and an ifenprodil plus ketamine combination (0.03mg kg-1 and 0.3mg kg-1, respectively; IKT). Dogs were anesthetized with propofol (5mg kg-1 intravenously) and a subarachnoid needle was placed between the 5th and 6th lumbar vertebrae. Five minutes after subarachnoid injection of KT or IKT, an incision including cutaneous and subcutaneous tissues was made on the common pad of one hind limb and was immediately closed with a simple interrupted suture pattern. The dogs were treated again 20 days later, using the contralateral pad and the opposite treatment. Sedation score (SS), lameness score (LS), heart rate (HR), respiratory rate (fR), and mechanical nociceptive threshold using von Frey filaments, were evaluated before anesthesia and at 1, 1.5, 2, 3, 4, 8, 12, and 24 hours after subarachnoid injection. There were no differences in SS, LS, HR or fR between treatments. The intensity of hyperalgesia was higher in KT than in IKT for 24 hours. The anti-hyperalgesic effect of IKT remained without statistical significant difference between 1 and 24 h. Prior subarachnoid administration of ifenprodil enhances the anti-hyperalgesic effect of subarachnoid ketamine in dogs. Ifenprodil can be co-administrated with ketamine to enhance its anti-hyperalgesic effect and to reduce acute post-incisional hyperalgesia without motor impairment and sedation.

Visualization of regional cerebrospinal fluid flow with a dye injection technique in focal arachnoid pathologies

Surgical lysis of the thickened arachnoid membrane is the first choice of treatment in spinal arachnoid pathologies that cause flow disturbances or blockage of CSF. However, it is important to consider that while extensive lysis of the arachnoid may temporarily provide a wide pathway for CSF, an extensive lytic procedure may later cause secondary adhesion. Thus, it is ideal for the proper extent of the arachnoid lysis to be determined after careful analysis of regional CSF flow. The authors report their limited experience with intraoperative visualization of CSF flow in spinal arachnoid pathologies. Two patients with a dorsal arachnoid web (DAW) with cervical syringomyelia and 1 patient with focal adhesive arachnoiditis causing edema of the spinal cord were surgically treated at the authors' institution between 2007 and 2013. In all cases, the presence of a DAW or focal adhesive arachnoiditis was suspected from the findings on MRI, namely 1) an indentation on the upper thoracic spinal cord and 2) syringomyelia and/or edema of the spinal cord above the indentation. Exploratory surgery disclosed a transversely thickened arachnoid septum on the dorsal side of the indented cord. To prove blockage of the CSF by the septum and to decide on the extent of arachnoid lysis, regional CSF flow around the arachnoid septum was visualized by subarachnoid injection of gentian violet solution close to the web. Injected dye stagnated just close to the arachnoid septum in all cases, and these findings documented CSF blockage by the septum. In 2 cases, a 2-minute observation showed that the injected dye stayed close to the web without diffusion. The authors performed not only resection of the web itself but also lysis of the thickened arachnoid on both sides of the spinal cord to make a CSF pathway on the ventral side. In the third case, the dye stagnated close to the web at first but then diffused through the nerve root to the ventral CSF space. The lysis procedure was completed after exclusive removal of the dorsal web. Postoperative MR images confirmed reduction of the syrinx and/or improvement of the edema in all cases, suggesting that the extent of arachnoid lysis was optimal in each case. No adverse effect was observed after subarachnoid injection of gentian violet. The authors believe that their technique of visualizing regional CSF flow will be helpful to decide the optimal extent of lysis in some local arachnoid pathologies.