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Magnetic Resonance Imaging of Cerebrospinal Fluid Leak and Tamponade Effect of Blood Patch in Postdural Puncture Headache

Vakharia, Shermeen B. MD; Thomas, P. Sebastian MD; Rosenbaum, Arthur E. MD; Wasenko, John J. MD; Fellows, David G. MD

Regional Anesthesia and Pain Management
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This prospective study examined the efficacy of magnetic resonance imaging (MRI) in visualizing cerebrospinal fluid (CSF) leak in patients with postdural puncture headache (PDPH) and determining the spread of the blood patch in the epidural space and the extent of tamponade on the thecal sac.After obtaining institutional review board approval, five patients with symptomatic PDPH after 3 days of failed conservative treatment were included in this study. MRI using proton density (PD) and T2-weighted imaging was performed on all patients and CSF flow studies were done on one patient. All patients received 20 mL of blood in the epidural space. They remained supine for 45 min, and repeat MRI studies were performed. Extent of the spread of blood in the epidural space was measured. A visual analog scale of 0-10 was used to evaluate the headache. All patients had severe postural headache with nausea/vomiting. Preblood patch MRI showed extrathecal CSF and hemosiderosis indicating the site of dural puncture in four patients. The postprocedure MRI demonstrated the blood patch as a large extradural collection with anterior displacement of the thecal sac, the mean spread being 4.6 intervertebral spaces. The tamponade effect of the blood patch was observed on PD, T2-weighted, and CSF flow images. All patients experienced immediate resolution of their symptoms. This study suggests that using MRI, the site of the CSF leak, the tamponade effect of the blood patch, and its spread in the epidural space can be documented.

(Anesth Analg 1997;84:585-90)

Departments of (Vakharia, Thomas, Fellows) Anesthesiology and (Rosenbaum, Wasenko) Radiology, SUNY Health Science Center at Syracuse, Syracuse, New York.

Accepted for publication November 13, 1996.

Address correspondence and reprint requests to P. Sebastian Thomas, MD, SUNY Health Science Center at Syracuse, 750 East Adams St., Syracuse, NY 13210.

Spinal headache was first described by August Bier in 1898 [1]. Over the years, the use of increasingly small-gauge needles, as well as the popularity of pencil-point needle tips, has dramatically decreased the incidence of postdural puncture headache (PDPH) in patients who are less than 40 years of age [2]. Despite these advances, spinal anesthesia, accidental dural puncture during epidural anesthesia, and myelography continue to be the major causes of PDPH.

PDPH is usually transient, self-limiting, and responsive to intravenous or oral fluids, caffeine administration, analgesics, and bed rest [2]. When conservative therapy fails, epidural blood patch is considered the definitive treatment for PDPH. Despite the clinical efficacy of the epidural blood patch for PDPH, so far no study has been performed using noninvasive techniques to document cerebrospinal fluid (CSF) leak, and the effect of the blood patch on this leak, in patients with PDPH. This prospective study examined the efficacy of magnetic resonance imaging (MRI) in visualizing CSF leak in patients with PDPH and the extent of tamponade caused by the blood patch on the thecal sac.

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Methods

After obtaining approval from our institutional review board and informed consent, five patients were included in the study. All patients had clinically documented symptomatic PDPH that had failed to respond to 3 days of conservative management with intravenous or oral fluids, bed rest, and analgesics. One patient had accidental dural puncture with an 18-gauge Touhy needle during epidural anesthesia, and three patients developed PDPH after spinal anesthesia with 22-gauge and 26-gauge Quincke needles and a 25-gauge needle with unknown needle tip. One patient had postmyelography PDPH after dural puncture was performed with a 20-gauge needle. In all patients, PDPH occurred within 72 h of dural puncture. The clinical criteria used to assess the patients pre- and postblood patch included the visual analog scale of 0-10 (0 was no headache and 10 represented the worst headache ever) for evaluation of the severity of the headache in the supine and sitting positions and associated nausea and vomiting (Table 1).

Table 1

Table 1

Prior to performing the blood patch, MRI of the lumbar spine was obtained using proton density (PD) and T2-weighted (T2W) imaging. CSF flow studies were also performed in one patient. The primary plane used was sagittal, and the parameters were spin echo. After the MRI studies, 20 mL of autologous blood was injected in the lumbar epidural space under strict aseptic conditions with the patient in the lateral recumbent position. The patient remained supine for a minimum of 45 min. Repeat PD and T2W imaging was done in sagittal and parasagittal planes. Gradient echo parameters were used to sense susceptibility effects in the detection of hemoglobin and its products. The patients were observed in the hospital for 24 h and then discharged home when they were pain free. The follow-up assessment was performed at the office 1 wk later.

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Results

Three women and two men participated in the study. Their ages ranged from 31 to 44 years. All patients had severe postural headache associated with nausea and vomiting, which resolved immediately after the placement of the epidural blood patch. Preblood patch PD and T2W imaging showed extradural local static fluid collection in two patients (Figure 1). The level of fluid collection correlated with the clinical level of dural puncture. In two other patients, hemosiderosis (fluid and tissue stained by old blood) along the posterior margin of the thecal sac with only mild compressive effect was demonstrated (Figure 2A and Figure 2B). There was no clinical evidence of thecal sac displacement or nerve compression in any of these patients. These foci of hemosiderosis in the posterior epidural space indicate that bleeding had occurred from an epidural vein during the initial puncture, even though there was no clinical evidence of bleeding at that time. In one patient, the level of hemosiderosis was one level higher than the clinically estimated level of lumbar puncture. This could be explained by an error in estimating the vertebral level based on palpation of spinous processes. In four of five patients, there was evidence of CSF leak or dural puncture.

Figure 1

Figure 1

Figure 2

Figure 2

Postblood patch PD and T2W images demonstrate the blood patch as a large collection of deoxyhemoglobin, mainly in the posterior epidural space, correlating with the initial level of dural puncture (Figure 3A and Figure 3B). The mean spread (+/- SD) of the 20-mL blood patch was 4.6 +/- 0.9 intervertebral spaces (Table 1). This was approximately 3.5 intervertebral spaces above and 1 intervertebral space below the level of injection. Anterior layering of blood was seen in one patient (Figure 3C). T2W imaging in the axial plane showed the blood patch displacing the thecal sac anteriorly. This tamponade effect is demonstrated more impressively by the CSF flow studies, which show the extent of posterior compression of the thecal sac (Figure 4).

Figure 3

Figure 3

Figure 4

Figure 4

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Discussion

MRIs are pictorial representations depicting the location of fat and water in tissues, sampled as thin sections through the human body. This technology relies on the nuclear magnetic resonance phenomenon and requires that the patient be placed in a strong magnetic field. Harmless radiofrequency pulses are applied, allowing detection of the amount and the location of hydrogen-containing material (fat and water) in a person's body [3,4]. A computer processes the faint electrical signal arising from the hydrogen nuclear magnetization into images that can be viewed on a computer monitor or printed onto film. The diagnostic value of MRI comes from its ability to discriminate different kinds of soft tissue. In part, this is possible because of the variations of fat and water content in the tissues but also because of the different rates at which the nuclear magnetization grows in tissues and the rates at which the detectable signals disappear with time. These growth and decay rates are termed T1 and T2, respectively. Radiologists have coined the terms T1-weighted image, T2W image, PD image, etc., to indicate the variables used to collect the image.

A T1-weighted image results when the radiofrequency pulses used to generate imaging signals are closely spaced in time. The parameter TR is used to report this time spacing, and if it is less than 800 milliseconds, the image is said to be T1-weighted. Tissues such as fat, which recover their nuclear magnetization quickly, will appear with bright intensity on these images.

If the TR parameter is set to be long (i.e., greater than 2200 milliseconds) during image collection and the signal is collected immediately after the radiofrequency pulse, a PD image is produced [5].

T2W images are produced by allowing the electrical signal to decay for a short period of time before collecting it in the computer. The time between the radiofrequency pulse generating the signal and its actual detection is called TE. If this parameter is set to be greater than 60 milliseconds, a T2W image results.

There are other variations of the variables in MRI that allow the detection of flowing material, permitting magnetic resonance angiography [5]. Gradient echo sequences permit more rapid data collection, making possible three-dimensional imaging protocols with more 100 slices, each only 1 mm thick.

The brain and the spinal cord are surrounded by 150 mL of CSF. Approximately 50 mL of CSF is formed daily, most of which is secreted by choroid plexuses in the ventricles and absorbed by arachnoidal villi in the arachnoidal granulations of the venous sinuses. The CSF pressure is maintained at an average of 10 mm Hg [7]. The etiology of PDPH is attributed to the effect of postdurally related decreases in CSF pressure caused by the persistent leak of CSF from the dural hole [1,8,9]. The loss of CSF causes the brain to descend when the patient assumes the upright position, thus stretching the pain-sensitive meninges and resulting in a headache. In animal studies, investigators have shown that blood clots epidurally and seals the dural hole, thereby stopping the CSF leak [10,11].

In our study, CSF leak was demonstrated on MRI as focal accumulation of clear or blood-stained fluid extrathecally in four of five patients. Interestingly, in two patients, we noted blood in the posterior margin of the thecal sac demonstrated as hemosiderosis on the preblood patch MRI. One of these patients received spinal anesthesia, and the other received epidural anesthesia with accidental dural puncture. Neither of these two patients showed any evidence of bleeding while the initial block was being performed.

In 1960, Gormley [12] reported the injection of autologous blood for controlling PDPH. He injected only 2-3 mL of autologous blood into the epidural space and reported relief of the headache. Since then, investigators have demonstrated that higher success rates can be achieved with larger volumes of blood [13-15]. Crawford [13,14] reported a 70% success rate with 6-15 mL of blood. The success rate increased to 98% when he increased the amount of blood to 20 mL. In our study, 20 mL of blood was injected in all patients with complete resolution of symptoms and no recurrence of the headache. This volume produced significant compression of the thecal sac as it spread over the area of the previous dural puncture. Its appearance on MRI supports the theory that the blood patch works by forming a dural tamponade that occludes the needle hole. The epidural space is expanded and the subarachnoid space relatively contracted, thus increasing the CSF pressure. This mechanism accounts for the immediate resolution of headache after placement of an epidural blood patch. Two reports in the British literature by Griffiths et al. [16] and Beards et al. [17] describe a similar appearance of the epidural blood patch on MRI. In the first case report published by them, the preblood patch MRI scan using T1-weighted images did not demonstrate extrathecal CSF or hemosiderosis. Also contrary to their observation, we did not notice subarachnoid extension of blood in any of our patients. We did, however, find extension of the blood anteriorly in one patient. Their second study examined the MRI appearance of the blood patch up to 18 hours after patching [17]. An MRI scan was not performed prior to the placement of the blood patch; therefore, no CSF leak was demonstrated.

Postblood patch MRI demonstrated that the mean spread of the blood patch in the epidural space was 4.6 +/- 0.9 intervertebral levels. Most of the blood spread in the cephalad direction. This cephalad spread correlates with the findings in three prior studies, which described the spread of the blood patch using technetium-labeled red cells or MRI [15-17]. CSF flow studies, when positive, aid in better defining thecal compression, as shown in our study. Investigators have previously reported radicular pain and nerve root compression after the placement of the blood patch [18-20]. Even though there was MRI evidence of anterior displacement of descending nerves, none of our patients developed radicular symptoms during or after the injection of the blood patch.

Our study clearly demonstrates the tamponade effect of the 20-mL epidural blood patch, which we believe is responsible for the immediate resolution of PDPH. This was consistently shown by MRI studies. Due to cost and convenience, the use of MRI may not become a routine part of clinical management of PDPH. However, we believe that MRI and CSF flow studies can be used effectively as noninvasive tests to detect the site of CSF leak and to document the accurate placement of the blood patch.

The authors gratefully acknowledge Mary Corbett for her valuable contribution toward preparing this manuscript and Nicholas Szeverenyi, MD, Associate Professor of Radiology and Director of the MRI Laboratory, SUNY Health Science Center at Syracuse, NY, for the description of different MRI scans.

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