Surgical treatment of spontaneous intracranial hypotension

Dear Editor,

Spontaneous intracranial hypotension (SIH) is a clinical condition characterized by postural headache secondary to spontaneous leakage of cerebrospinal fluid (CSF) into the extradural space [1]. The cause of MM leakage is a longitudinal dural tear, meningeal diverticulum or a direct liquor-venous fistula (LVF) [2]. The disease was first described by the German neurologist Georges Schaltenbrand in 1938 and named hypoliquorrhea. The most common and typical symptom is orthostatic headache, which worsens when standing. Cephalea may be accompanied by a number of concomitant symptoms.

Spontaneous intracranial hypotension is an underdiagnosed disease with a reported incidence of 5 per 100,000 population/year and a mean age of presentation of 40-50 years with a predominance of women affected (1.5 : 1) [1].

The patient, a 61-year-old woman, presented with a one-year history of tinnitus and headaches that were not severe but were associated with a change in position from the outset. There was no difficulty lying down and it appeared about an hour after verticalization. The cephalea gradually worsened and the intervals of possible verticalization shortened. Neurological examination was without pathological findings. MRI of the brain natively showed discrete bilateral hygromas, and a follow-up examination in 3 months with contrast agent administration also showed thickened meningeal envelopes confirming suspected SIH. MRI of the cervical, thoracic and lumbar spine was negative, with no evidence of MM leakage or epidural collection. The patient underwent application of an epidural blood plug at another site in the L3/4 space, but without any effect.

After our consultation, the patient was admitted for dynamic CT myelography (DCTM). The examination was performed in one time in the whole spine on both sides and abdomen due to the introduction of an external lumbar drainage into the L5/S1 space before the scan, which allowed fractionated application of iodine contrast agent intrathecally just before the scan in that position. DCTM diagnosed LVF in the Th7 root region on the right in the ipsilateral lateral position (Figure 1). The only incidental finding was a multilocular small root cyst. On examination, surgical revision was indicated, consisting of performing a partial hemilaminectomy of the Th7/8 on the right, treating the LVF with bipolar coagulation, and then dissecting it (Figure 2). The patient reported resolution of her complaints immediately after surgery. Preoperatively, she reported headache grade 8-10 according to the visual analogue scale, and postoperatively 0-1 with significantly improved quality of life and return to work.

The liquor-venous fistula was first described in 1974 in a patient with chronic postpunctional cephalea diagnosed by digital subtraction myelography (DSM) [3]. It was mentioned as a cause of SIH 40 years later by Schievink et al. in 2014 [4]. In contrast to SIH arising from dural tears, LVF does not result in a depot of MM in the epidural space, making diagnosis difficult. LVFs, due to the abnormal connection between the spinal subarachnoid space and the adjacent paraspinal veins, allow unregulated transfer of MM into the venous system, causing intracranial hypotension. It is thought that LVF may be the cause of SIH in up to 25% of cases. The flow of MM into the venous system is unidirectional, which is due to the fact that MM pressure is maintained at a higher level than venous pressure [5]. LVFs are typically localized in the thoracic spine with a maximum occurrence in the Th7-12 region, and less frequently occur in the lower cervical or upper lumbar region.

Spinal arachnoid granulations involved in MM uptake are most commonly found in the thoracic spine in the region of the nerve roots and are surrounded by the vertebral venous plexus. Although the exact mechanism of LVF formation is unknown, rupture of the arachnoid granulation is thought to be the initiating mechanism [5].

Patients with SIH should first undergo spinal canal imaging (mainly MRI) aimed at detecting epidural fluid. If no such epidural fluid is identified, the presence of LVF is highly suspected. The vast majority of cases of SIH due to LVF are associated with abnormalities on MRI of the brain -⁠ pachymeningeal saturation, distension of the venous plexuses, subdural collection, pituitary congestion, reduced width of the optic nerve sheath, and a picture of a drooping brain (caudal displacement of the basal structures of the brain and brainstem, descent of the cerebellar tonsils). The presence of at least one of these was detected in 91% of patients (most commonly distension of the veins and saturation of the meningeal envelope) [6].

Recently, several methods to detect LVF have been mentioned. One of them is fluoroscopy-based DSM with digital subtraction to detect the site of rapid MM leakage into the extradural space by real-time monitoring of intrathecal passage of contrast agent. Initially, the examination was performed in the prone position, but later it was found that far greater detection was obtained in the supine position (15 vs. 74%) with the head positioned lower, and this technique has now become standard [7]. Comparable results have also been achieved with DCTM showing hyperdense paraspinal veins correlating with LVF findings on DSM [8]. Unlike standard CT and MR myelography, DCTM allows localization of the dural sac leak detection even in cases where there is no accumulation of MM in the epidural space or, on the contrary, extrathecal myelographic contrast material is imaged in multiple stages due to rapid flow through the defect. The key factor for imaging the site of MM leakage is positioning the patient in the supine or prone position. The lateral position has approximately five times the yield compared with the supine position. In patients without epidural fluid collection findings on spinal MRI, LVF was found using DCTM in 50% of cases [8]. The advantage of DSM compared to DCTM is the acquisition of more subtraction images per unit time, which contributes to more accurate localization of the leak site, especially in cases of suspected rapid MM leak. The disadvantages are the higher technical complexity of the examination and the high demands on patient cooperation due to the risk of imperfect subtraction of images due to respiratory movements. For this reason, some authors recommend performing DSM under general anesthesia [8].

Conservative therapy is not effective in LVF, nor is the application of an epidural blood plug (long-term effect in only 4%). The application of fibrin glue appears to be more promising than the application of an epidural blood plug [9]. The standard therapy is surgical ligation of LVF, which is effective and safe. Most commonly, ligation of the entire nerve root with LVF or also treatment of the LVF with bipolar coagulation and its dissection or loading of an aneurysmal vascular clamp is used. Complete resolution of symptoms is described in about 70% of patients and partial improvement in another 20%. Recurrences are described in 6% of patients [9]. Endovascular treatment is also mentioned in the literature, where selective embolization of draining veins with Onyx was performed during spinal venography after vena azygos catheterization [10].

This case report shows that surgical treatment can be beneficial in the management of patients with SIH. It is important and essential to detect LVF using special imaging techniques and also to think of this alternative in patients with SIH without proven epidural fluid collection.

Grant support

This work was supported by the Ministry of Health -⁠ RVO (FNBr, 65269705).

Conflict of interest

The authors declare that they have no conflict of interest in relation to the subject of the study.

This is an unauthorised machine translation into English made using the DeepL Translate Pro translator. The editors do not guarantee that the content of the article corresponds fully to the original language version.