Variations of the CNS Venous System Mimicking Pathology: Spectrum of Imaging Findings

Lumbar intradural space reduction during the Valsalva maneuver observed using cine MRI and MR myelography: a single-case experimental study

BACKGROUND

Previous studies have shown that the Valsalva maneuver (VM) causes spinal canal object movements. We hypothesized that this occurs because of cerebrospinal fluid (CSF) flow generated from intradural space reduction. Previous studies using myelograms reported lumbar CSF space changes during inspiration. However, no similar studies have been conducted using modern MRI. Therefore, this study analyzed intradural space reduction during the VM using cine magnetic resonance imaging (MRI).

METHODS

The participant was a 39-year-old, healthy, male volunteer. Cine MRI involved fast imaging employing steady-state acquisition cine sequence during three resting and VM sets for 60 s each. The axial plane was at the intervertebral disc and vertebral body levels between Th12 and S1 during cine MRI. This examination was performed on 3 separate days; hence, data from nine resting and VM sets were available. Additionally, two-dimensional myelography was performed during rest and the VM.

RESULTS

Intradural space reduction was observed during the VM using cine MRI and myelography. The intradural space cross-sectional area during the VM (mean: 129.3 mm2; standard deviation [SD]: 27.4 mm2) was significantly lower than that during the resting period (mean: 169.8; SD: 24.8; Wilcoxon signed-rank test, P < 0.001). The reduction rate of the vertebral body level (mean: 26.7%; SD: 9.4%) was larger than that of the disc level (mean: 21.4%; SD: 9.5%; Wilcoxon rank sum test, P = 0.0014). Furthermore, the reduction was mainly observed on the ventral and bilateral intervertebral foramina sides at the vertebral body and intervertebral disc levels, respectively.

CONCLUSION

The intradural space was reduced during the VM, possibly because of venous dilatation. This phenomenon may be associated with CSF flow, intradural object movement, and nerve compression, potentially leading to back pain.

State-of-the-Art Imaging Techniques in Metastatic Spinal Cord Compression

Metastatic Spinal Cord Compression (MSCC) is a debilitating complication in oncology patients. This narrative review discusses the strengths and limitations of various imaging modalities in diagnosing MSCC, the role of imaging in stereotactic body radiotherapy (SBRT) for MSCC treatment, and recent advances in deep learning (DL) tools for MSCC diagnosis. PubMed and Google Scholar databases were searched using targeted keywords. Studies were reviewed in consensus among the co-authors for their suitability before inclusion. MRI is the gold standard of imaging to diagnose MSCC with reported sensitivity and specificity of 93% and 97% respectively. CT Myelogram appears to have comparable sensitivity and specificity to contrast-enhanced MRI. Conventional CT has a lower diagnostic accuracy than MRI in MSCC diagnosis, but is helpful in emergent situations with limited access to MRI. Metal artifact reduction techniques for MRI and CT are continually being researched for patients with spinal implants. Imaging is crucial for SBRT treatment planning and three-dimensional positional verification of the treatment isocentre prior to SBRT delivery. Structural and functional MRI may be helpful in post-treatment surveillance. DL tools may improve detection of vertebral metastasis and reduce time to MSCC diagnosis. This enables earlier institution of definitive therapy for better outcomes.

Anomalous Frontal Extra-Axial Midline Traversing Vein as the Potential Source of Subarachnoid Hemorrhage

Extra-axial developmental venous anomalies (DVAs) are important anatomic structures that contribute to supplemental venous drainage of intracranial contents into the extracranial veins. We present the case of a 35-year-old woman with a sudden-onset severe headache, nausea, and vomiting who was found to have an atraumatic subarachnoid hemorrhage of left frontal convexity. Workup revealed a large anomalous extra-axial vein originating in the right frontal area, traversing the left frontal region, penetrating the left frontal bone just above the supraorbital foramen with likely drainage into the left external jugular vein. This vein could not be classified as an emissary vein given the lack of direct communication with the superior sagittal sinus anterior portion, which was found to be hypoplastic. This case report adds to the literature a description of a previously unreported midline traversing frontal extra-axial vein directly draining frontal lobes with a potential implication in an atraumatic subarachnoid hemorrhage of frontal convexity.

Hirayama-like disease in the thoracic spine

Hirayama disease is a cervical flexion myelopathy that typically causes upper extremity weakness in young male patients. We present two male patients (age 15 and 29) with MRI findings of thoracic ligamentous laxity similar in appearance to Hirayama disease. However, patients presented with atypical symptoms, specifically back pain and paresthesia of the upper and/or lower extremities, likely correlating to the abnormal thoracic spinal levels involved. Flexion/extension MRI sequences demonstrated the forward displacement of the dorsal dura and compression the thoracic cord with prominence of the posterior epidural space and venous plexus. Follow-up MRAs were negative for a spinal vascular malformation. Patients were managed conservatively with no surgical intervention. Clinical history, thoracic MRI, and follow-up flexion and angiographic imaging sequences may help confirm a diagnosis of Hirayama-like thoracic ligamentous laxity.

Spinal anastomosed remnant imprints of vertebral veins linking the transverse foramina: a case report of a novel anatomic variant of the cervical venous plexus

PURPOSE

Despite various postulated classifications attempting to simplify the complex angioarchitecture of the cervical spine, the nomenclature of spinal variants and lesions remains inconsistent. Knowledge of variations in the anatomy of the vertebral veins will assist in avoiding complications during neck surgery and procedures such as vertebroplasty. In addition, venous variants may act as a route for the spread of infection, emboli, or metastases. Therefore, we report a novel variant encountered at our institution in this case report.

METHODS

We coincidentally discovered an original anatomical variant of the cervical venous plexus linking the transverse foramina in a Saudi man.

RESULTS

We termed the variant "spinal anastomosed remnant imprints" (SARI), guided by the second edition of Terminologia Embryologica, a project of the Federative International Programme for Anatomical Terminology. This variant anastomoses with the vertebral veins at the same level, forming segmented osseous impressions. It shares a topographical relationship with the embryonic anterior cardinal veins, which normally regress in the prenatal period. We hypothesize that these intersegmental anastomosing veins do not always regress and may persist into adulthood, with individualized variations of the venous circulation.

CONCLUSION

This report highlights an important finding of interpersonal anatomical variation of veins in the cervical spine, discovered with the aid of advanced imaging to distinguish it from pathological conditions. This will be of assistance to radiologists, anatomists, and clinicians in decision-making and to surgeons in planning for neck surgery.

Structure and function of the perivascular fluid compartment and vertebral venous plexus: Illumining a novel theory on mechanisms underlying the pathogenesis of Alzheimer's, cerebral small vessel, and neurodegenerative diseases

Blood dynamically and richly supplies the cerebral tissue via microvessels invested in pia matter perforating the cerebral substance. Arteries penetrating the cerebral substance derive an investment from one or two successive layers of pia mater, luminally apposed to the pial-glial basal lamina of the microvasculature and abluminally apposed to a series of aquaporin IV-studded astrocytic end feet constituting the soi-disant glia limitans. The full investment of successive layers forms the variably continuous walls of the periarteriolar, pericapillary, and perivenular divisions of the perivascular fluid compartment. The pia matter disappears at the distal periarteriolar division of the perivascular fluid compartment. Plasma from arteriolar blood sequentially transudates into the periarteriolar division of the perivascular fluid compartment and subarachnoid cisterns in precession to trickling into the neural interstitium. Fluid from the neural interstitium successively propagates into the venules through the subarachnoid cisterns and perivenular division of the perivascular fluid compartment. Fluid fluent within the perivascular fluid compartment flows gegen the net direction of arteriovenular flow. Microvessel oscillations at the central tendency of the cerebral vasomotion generate corresponding oscillations of within the surrounding perivascular fluid compartment, interposed betwixt the abluminal surface of the vessels and internal surface of the pia mater. The precise microanatomy of this most fascinating among designable spaces has eluded the efforts of various investigators to interrogate its structure, though most authors non-consensusly concur the investing layers effectively and functionally segregate the perivascular and subarachnoid fluid compartments. Enlargement of the perivascular fluid compartment in a variety of neurological disorders, including senile dementia of the Alzheimer's type and cerebral small vessel disease, may alternately or coordinately constitute a correlative marker of disease severity and a possible cause implicated in the mechanistic pathogenesis of these conditions. Venular pressures modulating oscillatory dynamic flow within the perivascular fluid compartment may similarly contribute to the development of a variety among neurological disorders. An intimate understanding of subtle features typifying microanatomy and microphysiology of the investing structures and spaces of the cerebral microvasculature may powerfully inform mechanistic pathophysiology mediating a variety of neurovascular ischemic, neuroinfectious, neuroautoimmune, and neurodegenerative diseases.