Spontaneous absorption of osteophytic calcification associated with chronic dural tear and ventral spinal CSF leak

Abstract

Spontaneous intracranial hypotension (SIH) is associated with cerebrospinal fluid (CSF) hypovolemia, often from a traumatic dural tear from a calcified spinal osteophyte. Visualizing osteophytes on CT imaging can guide decision making on candidate leak sites. We report the atypical case of a 41-year-old woman whose ventral CSF leak was associated with an osteophyte that resorbed over an 18-month period. Full workup and treatment were delayed due to unexpected pregnancy and completion of gestational cycle with delivery of a healthy term infant. The patient initially presented with persistent orthostatic headaches with nausea and blurred vision. Initial MRI suggested brain sagging among other findings consistent with SIH. CT myelogram showed an extensive thoracic CSF leak with a prominent ventral T11–T12 osteophyte and multiple small disc herniations. The patient did not respond to epidural blood patches and deferred additional imaging due to her pregnancy. CT myelography performed 5 months post-partum showed an absence of the osteophyte; a follow-up digital subtraction myelogram performed 10 months post-partum showed evidence of source leak at T11–T12 level. T11–T12 laminectomy visualized and repaired a 5 mm ventral dural defect with symptom resolution. This report highlights the potential for a resorbed osteophyte to be the causative agent for long-standing dural tears that do not show visible calcifications on myelography.

Introduction

Spontaneous intracranial hypotension (SIH) is a condition that is caused by spinal cerebrospinal fluid (CSF) leaks. ¹ The estimated community prevalence is 4.3 people per 100,000 with a 2:1 female predominance though this is likely underestimated because of a lack of widespread recognition. ² Structural weakness of the spinal meninges is the major contributing factor; SIH is associated with multiple connective tissue disorders such as Marfan’s syndrome, Ehlers-Danlos syndrome type II, and autosomal dominant polycystic kidney disease.^1–5 Additionally, approximately one-third of SIH patients can attribute minor to moderate trauma as a precipitating incident to their symptoms, suggesting that mechanical forces may contribute as well.^1,4 These factors are well-known to predispose patients to CSF leak. ¹

Spontaneous CSF leaks may be classified by three major etiologies: dural tear (Type 1), meningeal diverticula (Type 2), and direct CSF-venous fistula (Type 3). ⁴ In Type 1 leaks, SIH is associated with extradural, degenerative conditions of the spine such as disc protrusions or osteophytes.^1,2,5 Osteophytes are calcified outgrowths of bone that are commonly associated with osteoarthritis. Endplate disc-osteophytes can produce tears in the thecal sac that result in very rapid CSF leakage, leading to CSF hypovolemia. ⁵ As a result, the presence of osteophytes on myelography can be a helpful indicator toward the etiology and location of a suspected CSF leak, especially for fast CSF leaks within the thoracic region. ⁵

We present a 41-year-old woman whose CSF leak was associated with a ventral osteophyte that resorbed over an 18-month period, which included a complete gestational cycle. This phenomenon has only been described once before. ⁶ Identification of the dural tear site is challenging, and review of the prior CT myelogram studies may help to assess osteophyte location as a therapeutic target.

Case presentation

A 41-year-old woman with a history of migraine without aura presented with sudden onset of persistent, orthostatic headache with blurred vision and nausea. Headache was triggered by standing upright and coughing, and relieved with lying supine for 2–8 min. She was a professional powerlifter, and while there were no provocative maneuvers at the exact time of onset, she was weightlifting 1 week prior. Initial MRI brain showed no focal abnormality but noted cerebellar tonsils were mildly low lying. Conventional CT myelography showed a rapid thoracic leak with possible sites including a prominent ventral T11–T12 osteophyte (Figure 1(a) and (b)) as well as small disc herniations at T3–T4, T5–T6, and T8–T9. She was treated empirically with two epidural blood patches at T10–T11 and L2–L3 (20 cc total) without sustained clinical benefit. Follow-up dynamic CT myelography was deferred after discovering she was pregnant. During gestation, patient reported gradual temporization of symptoms while treated with repeated greater occipital and trigeminal nerve blocks, and her child was delivered full-term via a scheduled C-section without complications. Her headache gradually returned after 2 months post-partum, though her follow-up MRI brain was unrevealing without sequelae of SIH, and she received another epidural blood patch at T11–T12 which provided relief for approximately 3 months. At this time, spinal MRI showed persistence of extradural CSF collection; however, conventional digital subtraction myelograms of cervical, thoracic, and lumbar spine could not localize a CSF leak site. CT myelography showed absence of the T11–T12 osteophyte (Figure 1(c)). A T7–T8 laminectomy and surgical exploration were performed, and ventral dural thinning was closed without complication. There was resolution of the extradural CSF collection; however, the patient’s symptoms returned within 1 month. At this time, digital subtraction myelography was repeated and showed ventral CSF leak at T11–T12 (Figure 2), which was correlated to the absent osteophyte in original imaging (Figure 1(c)). A laminectomy at T11–T12 was subsequently performed, where a 5 mm ventral dural tear was visualized and repaired (Figure 3). After the first day of post-operative care, patient reported paroxysmal pain localized to her hip and upper buttocks along with mild headaches; however, both these symptoms abated after a 1-week steroid course. She returned to the workforce after 3 months, and over the past year, she has reported no recurrence of headaches.

Figure 1.

(a) Axial CT myelogram imaged 15 weeks, 2 days after symptom onset, showing ventral T11–T12 osteophyte (arrow) with slight eccentricity to the left. (b) Sagittal CT myelogram view showing ventral T11–T12 osteophyte (arrow). (c) Axial thoracic CT myelogram imaged 78 weeks after symptom onset (23 weeks, 3 days post-partum), showing absence of the osteophyte.

Figure 2.

Lateral thoracic digital subtraction myelogram (post-subtraction) done in prone position shows the extravasation of contrast dye (white arrow) at T11–T12 level. Contrast dye is normally visible intrathecally (black arrow).

Figure 3.

Intraoperative T11–T12 laminectomy photograph showing 5 mm ventral dural tear (black arrow).

Discussion

Spontaneous intracranial hypotension is caused by reduction of CSF fluid volume associated with an extradural spinal CSF leak. For Type 1 CSF leaks associated with dural tears, ventrally located osteophytes and/or calcified disks are the most common etiologies. ⁴ They are a frequent cause of SIH in patients who are refractory to conservative treatment and EBPs.^1,7 Myelography remains the gold-standard imaging modality to identify potentially causative spurs and to accurately localize the level and extent of a CSF leak.^1,3,7 However, a significant number of patients do not show calcified lesions on myelography despite confirmed presence of a dural tear intraoperatively.^4,6

This patient’s absorbed osteophyte offers a partial explanation for this absence. Her pre-partum disease course was not unusual for an osteophyte-associated CSF leak. According to the International Classification of Headache Disorders (ICHD) guidelines, the patient’s initial presentation met the diagnostic criteria for low CSF pressure-attributed headaches, as she demonstrated orthostatic headaches with accompanying visual disturbances, and initial imaging showed evidence of rapid thoracic CSF leakage (and compatible brain imaging abnormalities).^1,8,9 Her symptoms were recalcitrant to conservative management and three thoracic EBPs; osteophyte-associated SIH has a lower success rate than other indications for EBPs such as post-dural puncture headaches. ⁹ However, the patient’s gap in imaging due to her unexpected pregnancy provided time for the ventral T11–T12 osteophyte to absorb, granting an unusual opportunity to capture the appearance and disappearance of the osteophyte over serial myelograms. This absorption was not fully appreciated during the first symptom recurrence (which resulted in T7–T8 laminectomy), but it was later considered a point of interest after review of the original myelography 1 month later, which ultimately led to intraoperative tear confirmation and a successful repair without recurrence. While the literature supports that osteophytes may spontaneously resolve on their own, this case report lends credence to the hypothesis that osteophyte absorption may occur often enough to comprise some of the dural tears that show no calcifications on myelography. This phenomenon has been documented in a previous case report. ⁶ The current report provides supporting evidence that absorbed osteophytes may be a more common etiology for dural tears than previously thought. It also emphasizes the importance of careful review of longitudinal myelography studies, as this imaging change was critical for dural tear site localization.

ORCID iD

Varun K Rohatgi https://orcid.org/0009-0008-2013-2461