Diagnosis and Treatment of Spontaneous Intracranial Hypotension: Role of Epidural Blood Patching

Purpose of Review

This review focuses on the challenges of diagnosing and treating spontaneous intracranial hypotension (SIH), a condition caused by spinal CSF leakage. It emphasizes the need for increased awareness and advocates for early and thoughtful use of empirical epidural blood patches (EBPs) in suspected cases.

Recent Findings

SIH diagnosis is hindered by variable symptoms and inconsistent imaging results, including normal brain MRI and unreliable spinal opening pressures. It is crucial to consider SIH in differential diagnoses, especially in patients with connective tissue disorders. Early EBP intervention is shown to improve outcomes.

Summary

SIH remains underdiagnosed and undertreated, requiring heightened awareness and understanding. This review promotes proactive EBP use in managing suspected SIH and calls for continued research to advance diagnostic and treatment methods, emphasizing the need for innovative imaging techniques for accurate diagnosis and timely intervention.

Evaluation of LY573144 (lasmiditan) in a preclinical model of medication overuse headache

BACKGROUND

Medication overuse is a significant issue that complicates the treatment of headache disorders. The most effective medications for the acute treatment of migraine all have the capacity to induce medication overuse headache (MOH). Novel acute migraine-specific treatments are being developed. However, because the mechanism(s) underlying medication overuse headache are not well understood, it is difficult to predict whether any particular acute medication will induce MOH in susceptible individuals. LY573144 (lasmiditan), a 5-HT_1F receptor agonist, has recently been shown to be effective in the acute treatment of migraine in phase 3 trials. The aim of this study is to determine whether frequent administration of lasmiditan induces behaviors consistent with MOH in a pre-clinical rat model.

METHODS

Sprague Dawley rats were administered six doses of lasmiditan (10 mg/kg), sumatriptan (10 mg/kg), or sterile water orally over 2 weeks and cutaneous allodynia was evaluated regularly in the periorbital and hindpaw regions using von Frey filaments. Testing continued until mechanosensitivity returned to baseline levels. Rats were then submitted to bright light stress (BLS) or nitric oxide (NO) donor administration and were again evaluated for cutaneous allodynia in the periorbital and hindpaw regions hourly for 5 hours.

RESULTS

Both lasmiditan and sumatriptan exhibited comparable levels of drug-induced cutaneous allodynia in both the periorbital and hindpaw regions, which resolved after cessation of drug administration. Both lasmiditan and sumatriptan pre-treatment resulted in cutaneous allodynia that was evoked by either BLS or NO donor.

CONCLUSIONS

In a pre-clinical rat model of MOH, oral lasmiditan, like sumatriptan, induced acute transient cutaneous allodynia in the periorbital and hindpaw regions that after resolution could be re-evoked by putative migraine triggers. These results suggest that lasmiditan has the capacity to induce MOH through persistent latent peripheral and central sensitization mechanisms.

Other Preventive Anti-Migraine Treatments: ACE Inhibitors, ARBs, Calcium Channel Blockers, Serotonin Antagonists, and NMDA Receptor Antagonists

PURPOSE OF REVIEW

Migraine causes more years of life lived with disability than almost any other condition in the world and can significantly impact the lives of individuals with migraine, their families, and society. The use of medication for the prevention of migraine is an integral component to reducing disability caused by migraine. There are many different drug classes that have been investigated and shown efficacy in migraine prophylaxis. This article examines several of the classes of medications that are used for migraine preventive treatment, specifically, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, calcium channel blockers, serotonin antagonists, alpha-adrenergic agonists, and N-methyl-D-aspartic acid receptor antagonists.

RECENT FINDINGS

There have been randomized control trials investigating medications in these drug classes since the most recent guidelines for migraine prevention in adults were published by the American Academy of Neurology, American Headache Society, and the Canadian Headache Society. In these investigations, enalapril, candesartan, and memantine all demonstrated efficacy for migraine prevention. The evidence for these and the aforementioned drug classes are reviewed. When oral medications are being selected for migraine prevention, comorbid and coexistent medical conditions, concomitant medications, patient preference, and pregnancy and breast-feeding plans should be considered. Within the drug classes discussed, memantine and candesartan have a moderate level of evidence for efficacy.

Imaging Post-Traumatic Headache

PURPOSE OF REVIEW

Headache is a frequent and debilitating symptom after mild traumatic brain injury, yet little is known about its pathophysiology and most effective treatments. The goal of this review is to summarize findings from imaging studies used during the clinical evaluation and research investigation of post-traumatic headache (PTH).

RECENT FINDINGS

There are no published recommendations or guidelines for when to acquire imaging studies of the head or neck in patients with PTH. Clinical acumen is required to determine if imaging is needed to assess for a secondary cause of headache which may have been precipitated or unmasked by the trauma. Several guidelines for when to image the patient with mild traumatic brain injury (mTBI) in the emergency setting consider headache among the deciding factors. In the research arena, imaging techniques including proton spectroscopy magnetic resonance imaging, diffusion tensor imaging, magnetic resonance morphometry, and functional neck x-rays have been employed with the goal of identifying diagnostic and prognostic factors for PTH and to help understand its underlying pathophysiologic mechanisms. Results indicate that changes in regional cortical thickness and damage to specific white matter tracts warrant further research. Future research should interrogate whether these imaging findings contribute to the classification and prognosis of PTH. Current research provides evidence that imaging findings associated with PTH may be distinct from those attributable to mTBI. A variety of imaging techniques have potential to further our understanding of the pathophysiologic processes underlying PTH as well as to provide diagnostic and prognostic indicators. However, considerable work must be undertaken for this to be realized.

Heparin cofactor II: discovery, properties, and role in controlling vascular homeostasis

Heparin cofactor II (HCII) is a serine protease inhibitor (serpin) found in high concentrations in human plasma. Despite its discovery >30 years ago, its physiological function is still poorly understood. It is known to inhibit thrombin, the predominant coagulation protease, and HCII-thrombin complexes have been found in plasma, yet it is thought to contribute little to normal hemostasis. However, thrombin has several other physiological functions, and therefore many biological roles for HCII need consideration. The unique structure and mechanism of action of HCII have helped guide our understanding of HCII. In particular, HCII binds many glycosaminoglycans (GAGs) such as heparin and heparin sulfate as well as several different polyanions to enhance its inhibition of thrombin. Distinctly, HCII is able to use the GAG dermatan sulfate for accelerated thrombin inhibition. Dermatan sulfate is found in high concentrations in the walls of blood vessels as well as in placental tissue. This knowledge has led to research indicating that HCII may play a protective role in atherosclerosis and placental thrombosis. Additionally, pharmaceuticals are being developed that use the dermatan sulfate activation of HCII for anticoagulation. Although much research is still needed to fully understand HCII, this humble protein may have significant impact in our medical future. This article reviews the laboratory history, protein characteristics, structure-activity relationships, protease inhibition, physiological function, and medical relevance of HCII in hopes of regenerating interest in this sometimes forgotten serpin.

Serpins in thrombosis, hemostasis and fibrinolysis

Hemostasis and fibrinolysis, the biological processes that maintain proper blood flow, are the consequence of a complex series of cascading enzymatic reactions. Serine proteases involved in these processes are regulated by feedback loops, local cofactor molecules, and serine protease inhibitors (serpins). The delicate balance between proteolytic and inhibitory reactions in hemostasis and fibrinolysis, described by the coagulation, protein C and fibrinolytic pathways, can be disrupted, resulting in the pathological conditions of thrombosis or abnormal bleeding. Medicine capitalizes on the importance of serpins, using therapeutics to manipulate the serpin-protease reactions for the treatment and prevention of thrombosis and hemorrhage. Therefore, investigation of serpins, their cofactors, and their structure-function relationships is imperative for the development of state-of-the-art pharmaceuticals for the selective fine-tuning of hemostasis and fibrinolysis. This review describes key serpins important in the regulation of these pathways: antithrombin, heparin cofactor II, protein Z-dependent protease inhibitor, alpha(1)-protease inhibitor, protein C inhibitor, alpha(2)-antiplasmin and plasminogen activator inhibitor-1. We focus on the biological function, the important structural elements, their known non-hemostatic roles, the pathologies related to deficiencies or dysfunction, and the therapeutic roles of specific serpins.