Spinal Cerebrospinal Fluid Leak Localization with Digital Subtraction Myelography: Tips, Tricks, and Pitfalls

Cerebrospinal fluid (CSF) leak can cause spontaneous intracranial hypotension (SIH) which can lead to neurologic symptoms, such as orthostatic headache. Over time, imaging techniques for detecting and localizing CSF leaks have improved. These techniques include computed tomography (CT) myelography, dynamic CT myelography, cone-beam CT, MRI, MR myelography, and digital subtraction myelography (DSM). DSM provides the highest sensitivity for identifying leak sites and has comparable radiation exposure to CT myelography. The introduction of the lateral decubitus DSM has proven invaluable in localizing leaks when other imaging tests have been inconclusive.

Role of four-dimensional computer tomography (4D-CT) in non-localising and discordant first-line imaging in primary hyperparathyroidism

BACKGROUND

Accurate preoperative localisation of parathyroid adenoma is imperative for the success of minimally invasive parathyroidectomy (MIP).

OBJECTIVE

Our study aimed to evaluate the role of four-dimensional computer tomography (4D-CT) scan as an imaging modality in patients with failed and discordant localisation reported in the first-line imaging modalities (ultrasonography and 99mTc-MIBI-SPECT/CT).

METHODS

This is a prospective cohort study performed at a university teaching centre from March 2013 to July 2021. All patients with primary hyperparathyroidism who had failed localisation by ultrasonography and 99mTc-MIBI-SPECT/CT (SpCT), or discordance between them, had 4D-CT performed in this study.

RESULTS

One hundred and two sporadic cases of pHPT with failed/discordant first-line imaging had 4D-CT imaging prior to parathyroidectomy. In 102 patients, 105 parathyroid adenomas were reported on histopathology. 4D-CT was able to localise 78% of them to the correct side and 64% to the correct quadrant in 102 patients, as compared with US (correct side 21%, correct quadrant 16%) and 99mTc-MIBI-SPECT/CT (correct side 36%, correct quadrant 31%). 4D-CT had a sensitivity, precision, accuracy and F1 score for correct quadrant localisation as 79%, 81%, 66% and 80%; and for correct side localisation as 82%, 98%, 80% and 89%, respectively. 4D-CT was able to identify three ectopic adenomas (two in superior mediastinum and one in the oesophageal wall) which were not detected on US or SpCT.

CONCLUSION

4D-CT was found to be sensitive and accurate in preoperative localising of the diseased parathyroid glands after failed/discordant US and SpCT. This led to more patients being offered MIP as the primary surgery and improved operative outcomes.

Postoperative Spinal Cerebrospinal Fluid-Venous Fistulas Associated With Dural Tears in Patients With Intracranial Hypotension or Superficial Siderosis-A Digital Subtraction Myelography Study

BACKGROUND

Postoperative spinal cerebrospinal fluid (CSF) leaks are common but rarely cause extensive CSF collections that require specialized imaging to detect the site of the dural breach.

OBJECTIVE

To investigate the use of digital subtraction myelography (DSM) for patients with extensive extradural CSF collections after spine surgery.

METHODS

A retrospective review was performed to identify a consecutive group of patients with extensive postoperative spinal CSF leaks who underwent DSM.

RESULTS

Twenty-one patients (9 men and 12 women) were identified. The mean age was 46.7 years (range, 17-75 years). The mean duration of the postoperative CSF leak was 3.3 years (range, 3 months to 21 years). MRI showed superficial siderosis in 6 patients. DSM showed the exact location of the CSF leak in 19 (90%) of the 21 patients. These 19 patients all underwent surgery to repair the CSF leak, and the location of the CSF leak could be confirmed intraoperatively in all 19 patients. In 4 (19%) of the 21 patients, DSM also showed a CSF-venous fistula at the same location as the postoperative dural tear.

CONCLUSION

In this study, DSM had a 90% detection rate of visualizing the exact site of the dural breach in patients with extensive postoperative spinal CSF leaks. The coexistence of a CSF-venous fistula in addition to the primary dural tear was present in about one-fifth of patients. The presence of a CSF-venous fistula should be considered if CSF leak symptoms persist in spite of successful repair of a durotomy.

The reversible impairment of behavioral variant frontotemporal brain sagging syndrome: Challenges and opportunities

Introduction

Due to loss of brain buoyancy, spontaneous spinal cerebrospinal fluid (CSF) leaks cause orthostatic headaches but also can cause symptoms indistinguishable from behavioral variant frontotemporal dementia (bvFTD) due to severe brain sagging (including the frontal and temporal lobes), as visualized on brain magnetic resonance imaging. However, the detection of these CSF leaks may require specialized spinal imaging techniques, such as digital subtraction myelography (DSM).

Methods

We performed DSM in the lateral decubitus position under general anesthesia in 21 consecutive patients with frontotemporal dementia brain sagging syndrome (4 women and 17 men; mean age 56.2 years [range: 31-70 years]).

Results

Nine patients (42.8%) were found to have a CSF-venous fistula, a recently discovered type of CSF leak that cannot be detected on conventional spinal imaging. All nine patients underwent uneventful surgical ligation of the fistula. Complete or near-complete and sustained resolution of bvFTD symptoms was obtained by all nine patients, accompanied by reversal of brain sagging, but in only three (25.0%) of the twelve patients in whom no CSF-venous fistula could be detected (P = 0.0011), and who were treated with non-targeted therapies.

Discussion

Concerns about a spinal CSF leak should not be dismissed in patients with frontotemporal brain sagging syndrome, even when conventional spinal imaging is normal. However, even with this specialized imaging the source of the loss of spinal CSF remains elusive in more than half of patients.

Spontaneous spinal cerebrospinal fluid-venous fistulas in patients with orthostatic headaches and normal conventional brain and spine imaging

OBJECTIVE

To determine the occurrence of cerebrospinal fluid (CSF)-venous fistulas, a type of spinal CSF leak that cannot be detected with routine computerized tomography myelography, among patients with orthostatic headaches but normal brain and spine magnetic resonance imaging.

BACKGROUND

Spontaneous spinal CSF leaks cause orthostatic headaches but their detection may require sophisticated spinal imaging techniques.

METHODS

A prospective cohort study of patients with orthostatic headaches and normal brain and conventional spine imaging who underwent digital subtraction myelography (DSM) to look for CSF-venous fistulas, between May 2018 and May 2020, at a quaternary referral center for spontaneous intracranial hypotension.

RESULTS

The mean age of the 60 consecutive patients (46 women and 14 men) was 46 years (range, 13-83 years), who had been suffering from orthostatic headaches between 1 and 180 months (mean, 43 months). DSM demonstrated a spinal CSF-venous fistula in 6 (10.0%; 95% confidence interval [CI]: 3.8-20.5%) of the 60 patients. The mean age of these five women and one man was 50 years (range, 41-59 years). Spinal CSF-venous fistulas were identified in 6 (19.4%; 95% CI: 7.5-37.5%) of 31 patients with spinal meningeal diverticula but in none (0%; 95% CI: 0-11.9%) of the 29 patients without spinal meningeal diverticula (p = 0.024). All CSF-venous fistulas were located in the thoracic spine. All patients underwent uneventful surgical ligation of the fistula. Complete and sustained resolution of symptoms was obtained in five patients, while in one patient, partial recurrence of symptoms was noted 3 months postoperatively.

CONCLUSION

Concerns about a spinal CSF leak should not be dismissed in patients suffering from orthostatic headaches when conventional imaging turns out to be normal, even though the yield of identifying a CSF-venous fistula is low.

Spinal CSF-Venous Fistulas in Morbidly and Super Obese Patients with Spontaneous Intracranial Hypotension

BACKGROUND AND PURPOSE

Spinal CSF-venous fistulas are increasingly recognized as the cause of spontaneous intracranial hypotension. Here, we describe the challenges in the care of patients with CSF-venous fistulas who are morbidly or super obese.

MATERIALS AND METHODS

A review was undertaken of all patients with spontaneous intracranial hypotension and a body mass index of >40 who underwent digital subtraction myelography in the lateral decubitus position to look for CSF-venous fistulas.

RESULTS

Eight patients with spontaneous intracranial hypotension with a body mass index  of >40 underwent lateral decubitus digital subtraction myelography. The mean age of these 5 women and 3 men was 53 years (range, 45 to 68 years). Six patients were morbidly obese (body mass indexes = 40.2, 40.6, 41, 41.8, 45.4, and 46.9), and 2 were super obese (body mass indexes = 53.7 and 56.3). Lumbar puncture showed an elevated opening pressure in 5 patients (26.5-47 cm H₂O). The combination of an elevated opening pressure and normal conventional spine imaging findings resulted in a misdiagnosis (midbrain glioma and demyelinating disease, respectively) in 2 patients. Prior treatment included surgical nerve root ligation for suspected CSF-venous fistula in 3 patients. Digital subtraction myelography demonstrated a CSF-venous fistula in 6 patients (75%). Rebound high-pressure headache occurred in all 6 patients following surgical ligation of the fistula, and papilledema developed in 3.

CONCLUSIONS

In our series, opening pressure was generally elevated in patients with morbid or super obesity. The yield of identifying CSF-venous fistulas with digital subtraction myelography in this patient population can approach that of the nonobese patient population. These patients may be at higher risk of developing rebound high-pressure headaches and papilledema.