Intrathecal Contrast-Enhanced Magnetic Resonance Imaging of Cerebrospinal Fluid Dynamics and Glymphatic Enhancement in Idiopathic Normal Pressure Hydrocephalus.

Idiopathic normal pressure hydrocephalus (iNPH) is a neurodegenerative disease, characterized by cerebrospinal fluid (CSF) flow disturbance. Today, the only available treatment is CSF diversion surgery (shunt surgery). While traditional imaging biomarkers typically assess CSF space anatomy, recently introduced imaging biomarkers of CSF dynamics and glymphatic enhancement, provide imaging of CSF dynamics and thereby more specifically reveal elements of the underlying pathophysiology. The biomarkers address CSF ventricular reflux grade as well as glymphatic enhancement and derive from intrathecal contrast-enhanced MRI. However, the contrast agent serving as CSF tracer is administered off-label. In medicine, the introduction of new diagnostic or therapeutic methods must consider the balance between risk and benefit. To this end, we performed a prospective observational study of 95 patients with iNPH, comparing different intrathecal doses of the MRI contrast agent gadobutrol (0.10, 0.25, and 0.50 mmol, respectively), aiming at the lowest reasonable dose needed to retrieve diagnostic information about the novel MRI biomarkers. The present observations disclosed a dose-dependent enrichment of subarachnoid CSF spaces (cisterna magna, vertex, and velum interpositum) with dose-dependent ventricular reflux of tracer in iNPH, as well as dose-dependent glymphatic tracer enrichment. The association between tracer enrichment in CSF and parenchymal compartments were as well dose-related. Intrathecal gadobutrol in a dose of 0.25 mmol, but not 0.10 mmol, was at 1.5T MRI considered sufficient for imaging altered CSF dynamics and glymphatic enhancement in iNPH, even though 3T MRI provided better sensitivity. Tracer enrichment in CSF at the vertex and within the cerebral cortex and subcortical white matter was deemed too low for maintaining diagnostic information from a dose of 0.10 mmol. We conclude that reducing the intrathecal dose of gadobutrol from 0.50 to 0.25 mmol gadobutrol improves the safety margin while maintaining the necessary diagnostic information about disturbed CSF homeostasis and glymphatic failure in iNPH.

A woman in her seventies with acute onset of blindness. / En kvinne i 70-årene med akutt blindhet.

BACKGROUND: Dural arteriovenous fistulae are among the most common causes of pulsatile tinnitus. Selective angiography can be necessary for a definitive diagnosis, but in rare cases has been reported to cause sudden cortical blindness. CASE PRESENTATION: We present a woman in her seventies for whom cerebral angiography revealed a dural arteriovenous fistula. Two hours after the angiography she experienced sudden bilateral blindness. A local cause of sudden visual loss was excluded by clinical examination, cerebral bleeding was excluded by CT scan, vascular spasms and occlusions were excluded by CT angiography and acute infarction over the bilateral parieto-occipital cortex was excluded by MRI. The CT scan did, however, show contrast enhancement in the visual cortex from the contrast given during the previously performed cerebral angiography. The patient's vision spontaneously recovered within six days after the angiography, with no residual neurological deficits in her subsequent clinical follow up. Surgery was later performed on her dural arteriovenous fistula, which successfully treated the pulsatile tinnitus. INTERPRETATION: Transient cortical blindness is a rare but dramatic complication after cerebral angiography, thought to be caused by the transient neurotoxic effects of iodine-containing contrast agents. When other causes of sudden blindness are excluded, the patient can be reassured about the excellent prognosis for this condition.

Heterotopic ossification and clinical outcome in nonconstrained cervical arthroplasty 2 years after surgery: the Norwegian Cervical Arthroplasty Trial (NORCAT).

PURPOSE: Heterotopic ossification is a phenomenon in cervical arthroplasty. Previous reports have mainly focused on various semiconstrained devices and only a few publications have focused on ossification around devices that are nonconstrained. The purpose of this study was to assess the occurrence of heterotopic ossification around a nonconstrained cervical device and how it affects clinical outcome 2 years after surgery. METHODS: Thirty-seven patients were included from a larger cohort of a randomized controlled trial (NORCAT) which compared single-level cervical arthroplasty with fusion. The occurrence of heterotopic ossification was assessed with a CT scan and two neuroradiologists determined its degree. For grading, we used the Mehren/Suchomel classification system (grade 0-4). The patients were divided by level of ossification, low grade (0-2) or high grade (3-4), and clinical outcomes were compared. Self-rated disability for neck and arm pain (Neck Disability Index), health-related quality of life (the Short Form-36 and EuroQol-5D), and pain (the Numeric Rating Scale 11) were used as clinical outcome measures. RESULTS: Heterotopic ossification was encountered in all patients 2 years after surgery. Complete fusion (grade 4) was found in 16 % of participants, and high-grade ossification (grade 3-4) occurred in 62 %. The remaining patients were classified as having low-grade ossification (grade 2). There were no differences in the clinical outcomes of patients with low- and high-grade ossification. CONCLUSION: High-grade heterotopic ossification and spontaneous fusion 2 years after surgery were seen in a significant number of patients. However, the degree of ossification did not influence the clinical outcome.