Spontaneous intracranial hypotension diagnosis
Spontaneous intracranial hypotension diagnosis have evolved due to improved understanding of spontaneous intracranial hypotension pathophysiology and implementation of advanced myelography techniques. Farnsworth et al. synthesized recent updates and contextualize them in an algorithm for diagnosis and treatment of SIH, highlighting basic principles and points of practice variability or continued debate. This discussion includes finer points of SIH diagnosis, spontaneous cerebrospinal fluid fistula classification systems, less common types and variants of CSF leaks, Brain MRI Bern scoring for intracranial hypotension diagnosis, potential spontaneous intracranial hypotension complications, key technical considerations, and positioning strategies for different types of Dynamic CT myelography. 1).
The diagnosis of spontaneous intracranial hypotension or cerebrospinal fluid (CSF) hypovolemia syndrome requires a high index of suspicion and meticulous history taking, demonstration of low CSF pressure and/or neuroimaging features.
- any headache that developed in temporal relation to low CSF pressure or cerebrospinal fluid fistula or has led to its discovery
- low CSF pressure (< 6 cm of water) and/or evidence of CSF leakage on imaging
not better accounted for by another ICHD-III
Radiographic criteria are not required for diagnosis since no characteristic findings are seen in 20– 25% of patients.
The median delay from presentation to the diagnosis of SIH is 4 months.
This delay may be detrimental to patient outcomes. Therefore, brain MRI without and with contrast is recommended in patients with new-onset orthostatic headaches.
The diagnosis requires a high index of suspicion and meticulous history taking, demonstration of low CSF pressure and/or neuroimaging features.
The primary diagnostic factor relies on confirmation of cerebrospinal fluid leakage based on reduced spinal fluid pressure. Determining the specific leakage site is the most important issue for effective treatment but remains a difficult task. Although CT myelogram, radionuclide cisternography, and MRI are commonly performed in the diagnosis of CSF hypovolemia, these techniques can rarely identify the precise leakage site.
Therefore, an epidural blood patch is performed in the lumbar spine in many cases.
The identification of the site of CSF leak in the spinal canal can be very challenging. In some cases, the site cannot be identified.
Magnetic resonance imaging (MRI)
Intracranial pressure monitoring
A 31-year-old male, presented with subacute onset moderate occipital and sub-occipital headaches precipitated by upright posture and relieved on recumbency and neck pain for 2 years. There was no trauma, cranial/spinal surgery. Clinical examination was normal and CSF opening pressure and laboratory study were normal. Magnetic resonance imaging (MRI) brain showed thin subdural hygroma. Another patient, 41-year-old male presented with 1 month of subacute onset severe bifrontal throbbing orthostatic headaches (OHs). CSF opening pressure was normal. Contrast MRI brain showed the presence of bilateral subdural hygromas, diffuse meningeal enhancement, venous distension, sagging of the brain, and tonsillar herniation. We report two cases of “spontaneous OHs” with normal CSF pressures who were successfully treated with epidural blood patching after poor response to conservative management 3).
Repeated measurements of the optic nerve sheath diameter (ONSD) using B-mode sonography were performed before treatment initiation, during medical treatment, and during a course of repeated placement of epidural blood patches.
On admission, transorbital sonography revealed a decreased ONSD of 4.1 mm on the right and 4.3 mm on the left side. After 8 months of treatment with caffeine and computed tomography-guided epidural blood patches a gradual distension of the ONSD into the normal range was bilaterally observed (right: 5.2 mm; left: 5.3 mm).
The ultrasound-based evaluation of the optic nerve sheath may be helpful in detecting CSF hypovolemia and for determination of treatment effects. This report should be seen as a basis for future investigations on the sonographic assessment of the optic nerve sheath in diagnosis and treatment of intracranial hypotension 4).
Symptomatic patients with SIH showed a significant decrease of ONSD, as assessed by ultrasound, when changing from the supine to the upright position. Ultrasound assessment of the ONSD in two positions may be a novel, non-invasive tool for the diagnosis and follow-up of SIH and for elucidating the pathophysiology of SIH 5).