How do intracranial hypotension and neural foraminal stenosis correlate?

Relationship Between Intracranial Hypotension and Neural Foraminal Stenosis

There is no direct causal relationship between intracranial hypotension and neural foraminal stenosis, but spinal canal stenosis can potentially cause cerebrospinal fluid (CSF) leakage leading to intracranial hypotension in rare cases. 1

Pathophysiologic Mechanisms

• Intracranial hypotension is typically caused by CSF leakage through a dural defect, leaking meningeal diverticulum, or CSF-venous fistula, not by neural foraminal stenosis 2, 3
• The spine is the anatomical source of most symptomatic CSF leaks that cause intracranial hypotension, with leaks commonly occurring at the exit zones where cervical spinal roots leave the subarachnoid space 4, 5
• In rare cases, increased intradural pressure due to spinal canal stenosis can result in a dural tear, leading to CSF leakage into the epidural space and subsequently causing intracranial hypotension 1
• The pathophysiologic mechanisms of intracranial hypotension involve compensatory venodilation, downward traction on meninges, and loss of brain buoyancy leading to brain sagging 2

Clinical Presentation and Diagnostic Features

• Intracranial hypotension typically presents with orthostatic headaches that worsen when upright and improve when lying down 2
• Additional symptoms may include nausea, vomiting, tinnitus, photophobia, dizziness, and imbalance 2
• In severe cases, intracranial hypotension can lead to serious complications such as cerebral venous thrombosis (in approximately 2% of cases), seizures, and brain herniation 6, 2
• MRI is the preferred initial imaging modality for suspected intracranial hypotension, looking for findings such as pachymeningeal enhancement, brain sagging, subdural fluid collections, and engorgement of venous sinuses 4, 2

Case Evidence of Correlation

• A case report has documented intracranial hypotension with the C1-C2 sign (fluid collection between the spinous processes of C1 and C2) caused by spinal canal stenosis at C3/4 level 1
• In this case, increased intradural pressure due to spinal canal stenosis resulted in a dural tear, with CSF leaking into the epidural space and subsequently to the retrospinal region at C1-C2 level 1
• This suggests a potential mechanism where spinal canal stenosis can indirectly lead to intracranial hypotension through creating conditions for CSF leakage 1

Diagnostic Approach

• MRI head without and with IV contrast is recommended as the most useful initial evaluation for suspected intracranial hypotension 4
• Initial spine imaging should be MRI complete spine without IV contrast (or without and with contrast), optimized with fluid-sensitive sequences to detect epidural fluid collections and meningeal diverticula 4
• For patients with suspected intracranial hypotension who have spinal canal or foraminal stenosis, careful evaluation for CSF leaks should be performed, as the stenosis might be contributing to the leak 1

Management Implications

• Treatment of intracranial hypotension should focus primarily on management of the CSF leak 6
• First-line treatment is non-targeted epidural blood patch (EBP), which should be performed as early as possible 6
• In cases where intracranial hypotension is potentially related to spinal canal stenosis, addressing both the CSF leak and the stenosis may be necessary 1
• For patients with both conditions, a multidisciplinary approach involving neurology, neuroradiology, and neurosurgery is recommended to develop an appropriate treatment plan 6, 7

Important Considerations

• Approximately 20% of initial brain MRIs and 46-67% of initial spine imaging may be normal in patients with clinically suspected intracranial hypotension, making diagnosis challenging 4
• CSF pressure can be normal in some patients with intracranial hypotension, so imaging findings are crucial for diagnosis 4, 8
• Neural foraminal stenosis should be evaluated as a potential contributing factor to CSF leaks in patients with intracranial hypotension, particularly when conventional causes are not identified 1

While neural foraminal stenosis is not a common cause of intracranial hypotension, there is evidence suggesting that in rare cases, spinal canal stenosis can lead to increased intradural pressure, resulting in dural tears and subsequent CSF leakage causing intracranial hypotension.