MRI Findings of Spontaneous Intracranial Hypotension: Usefulness of Straight Sinus Distention

Spontaneous Intracranial Hypotension: A Review of Neuroimaging and Current Concepts

Spontaneous intracranial hypotension (SICH) is the emerging cause of orthostatic headache as it has been better recognized in recent years. SICH happens due to spinal cerebrospinal fluid (CSF) leak; however, the manifestations are predominantly cranial and hence imaging in SICH includes brain and spine. There are few characteristic brain imaging features to be concerned about to diagnose SICH in patients with vague symptoms or low clinical suspicion. Spine screening is recommended in these patients to assess spinal CSF leaks. While neuroradiologists play a significant role from the time of diagnosis to treatment of SICH, there is a need for all the general radiologists to be aware of the condition. Computed tomography myelogram and digital subtraction myelogram are performed for diagnostic and therapeutic management of SICH. There is a known risk for SICH recurrence in patients with sagittal longitudinal epidural collection and hence, targeted blood patch should be used instead of blind patch. Most importantly, slow mobilization is recommended following the patch to avoid recurrence.

Delayed recurrence of spontaneous intracranial hypotension syndrome mimicking a Chiari I malformation: Case report with a review of the literature

INTRODUCTION

Cerebellar tonsils descent seen on brain MRI is, along with other findings, a recognized radiological sign of possible spontaneous intracranial hypotension (SIH). The short-term outcome of SIH is usually favorable with symptoms improvement and reversibility of the low-lying tonsils. Nevertheless, data on the long-term outcome are lacking or inconsistent.

CASE REPORT

A 32-year-old woman presented to her general practitioner with a six months history of non-specific headaches. An MRI brain with gadolinium showed a 12mm tonsillar descent with no other remarkable findings. Headaches were initially managed conservatively as migraines. Following the onset of progressive upper back and shoulder pain at rest, nausea, photophobia and fogging in her vision, the patient was referred to our Department with a suspicion of symptomatic Chiari I malformation. After an in-depth anamnesis, it emerged a previous history of SIH, 14 years earlier, successfully treated conservatively in another center. A whole spine MRI confirmed the suspicion of recurrent SIH showing an anterior cervico-thoracic epidural fluid collection. The patient underwent an epidural blood patch with complete resolution of the symptoms and radiological signs.

DISCUSSION

To our knowledge, this case is the first report of delayed recurrence of a SIH successfully treated conservatively over 10 years earlier. The etiopathogenesis and management of this rarity with literature review is discussed.

CONCLUSION

An isolated cerebellar tonsil descent with no other remarkable findings on brain MRI and a previous history of SIH should always alert the clinician of a possible late recurrence of a CSF leak and avoid unnecessary Chiari I malformation surgical procedures.

Related Structures in the Straight Sinus: An Endoscopic Anatomy and Histological Study

Some structure might be encountered with endovascular procedures within the straight sinus and is not now readily seen on digital subtraction angiography (DSA). We investigated the morphological and histological characteristics of the straight sinus, chordae willisii (CW), and junction between the great cerebral vein (GCV) and straight sinus. A total of 22 cadaveric heads and 135 patients were analyzed with either anatomic dissection or neuroimaging. The morphological features of the CW and the junction between the GCV and straight sinus were analyzed by endoscope. The histology of the junction between the GCV and straight sinus was evaluated under the microscope with staining for elastic fiber, Masson’s, and immunohistochemistry. We found that fold, elevation, small bugle, or nodule and CW were detected by endoscope in the straight sinus. The most common type of CW was valve-like lamellae, which comprised 40.46% of all CW. Three different types of junctions between the GCV and straight sinus were identified: type 1 has folds in the GCV and elevation on the floor of the straight sinus; type 2 has folds and a small bugle; and type 3 presents with an intraluminal nodule located at the opening of the GCV. Compared with arachnoid granulation, the nodule consists of smooth muscle fibers and higher rate of elastic fibers. Understanding the detailed anatomy of the straight sinus may help surgeons to avoid procedural difficulties and to achieve higher success rate.

Spontaneous intracranial hypotension: key features for a frequently misdiagnosed disorder

Spontaneous intracranial hypotension (SIH) is a rare neurological condition caused by low cerebrospinal fluid (CSF) volume, most commonly due to a CSF leak. The most common presenting symptom is an orthostatic headache, but some patients may present with atypical neurological manifestations such as cranial nerve palsies, an altered mental status, and movement disorders, which complicate the clinical diagnosis. Therefore, the diagnosis is based on the combination of clinical signs and symptoms, neuroimaging, and/or a low cerebrospinal fluid pressure. In this review, we describe the wide variety of neurological manifestations and complications seen in patients with SIH as well as the most common features described on imaging studies, including both subjective and objective measurements, in order to lead the clinician to a correct diagnosis. The prompt and correct management of patients with SIH will help prevent the development of life-threatening complications, such as subdural hematomas, cerebral venous thrombosis, and coma, and avoid unnecessary invasive procedures.

In vivo detection of venous sinus distension due to intracranial hypotension in small animal using pulsed-laser-diode photoacoustic tomography

Intracranial hypotension (IH) is a pathophysiological condition of reduced intracranial pressure caused by low cerebrospinal fluid (CSF) volume due to dural injuries from lumbar puncture, surgery, or trauma. Understanding the prognosis of IH in small animal models is important to gain insights on the complications associated with it such as orthostatic headache, cerebral venous thrombosis, coma, and so forth. Photoacoustic tomography (PAT) offers a novel and cost-effective way to perceive and detect IH in small animal models. In this study, a pulsed laser diode (PLD)-based PAT imaging system was used to examine the changes in the venous sinuses of the rat brain due to IH, induced through CSF extraction. After the CSF extraction, an increase in the sagittal sinus area by ~30% and width by 40% ± 5% was observed. These results provide supportive evidence that the PLD-PAT can be employed for detecting changes in sagittal sinus due to IH in rat model.