Heterotopic ossification in a patient with paroxysmal sympathetic hyperactivity following multiple trauma complicated with vitamin D deficiency: a case report

Paroxysmal Sympathetic Hyperactivity After Acquired Brain Injury: An Integrative Review of Diagnostic and Management Challenges

Paroxysmal sympathetic hyperactivity (PSH) mainly occurs after acquired brain injury (ABI) and often presents with high fever, hypertension, tachycardia, tachypnea, sweating, and dystonia (increased muscle tone or spasticity). The pathophysiological mechanisms of PSH are not fully understood. Currently, there are several views: (1) disconnection theory, (2) excitatory/inhibitory ratio, (3) neuroendocrine function, and (4) neutrophil extracellular traps. Early diagnosis of PSH remains difficult, given the low specificity of its diagnostic tools and unclear pathogenesis. According to updated case analyses in recent years, PSH is now more commonly observed in patients with stroke, with tachycardia and hypertension as the main clinical manifestations, which is not fully consistent with previous data. To date, the PSH Assessment Measure tool is optimal for the early identification of PSH and stratification of symptom severity. Clinical strategies for the management of PSH are divided into three main points: (1) reduction of stimulation, (2) reduction of sympathetic excitatory afferents, and (3) inhibition of the effects of sympathetic hyperactivity on target organs. However, use of drugs and standards have not yet been harmonized. Further investigation on the relationship between PSH severity and long-term neurological prognosis in patients with ABI is required. This review aimed to determine the diagnostic and management challenges encountered in PSH after ABI.

Neurovascular coupling in bone regeneration

The mammalian skeletal system is densely innervated by both neural and vascular networks. Peripheral nerves in the skeleton include sensory and sympathetic nerves. The crosstalk between skeletal and neural tissues is critical for skeletal development and regeneration. The cellular processes of osteogenesis and angiogenesis are coupled in both physiological and pathophysiological contexts. The cellular and molecular regulation of osteogenesis and angiogenesis have yet to be fully defined. This review will provide a detailed characterization of the regulatory role of nerves and blood vessels during bone regeneration. Furthermore, given the importance of the spatial relationship between nerves and blood vessels in bone, we discuss neurovascular coupling during physiological and pathological bone formation. A better understanding of the interactions between nerves and blood vessels will inform future novel therapeutic neural and vascular targeting for clinical bone repair and regeneration.

Contemporary perspectives on heterotopic ossification

Heterotopic ossification (HO) is the formation of ectopic bone that is primarily genetically driven (fibrodysplasia ossificans progressiva [FOP]) or acquired in the setting of trauma (tHO). HO has undergone intense investigation, especially over the last 50 years, as awareness has increased around improving clinical technologies and incidence, such as with ongoing wartime conflicts. Current treatments for tHO and FOP remain prophylactic and include NSAIDs and glucocorticoids, respectively, whereas other proposed therapeutic modalities exhibit prohibitive risk profiles. Contemporary studies have elucidated mechanisms behind tHO and FOP and have described new distinct niches independent of inflammation that regulate ectopic bone formation. These investigations have propagated a paradigm shift in the approach to treatment and management of a historically difficult surgical problem, with ongoing clinical trials and promising new targets.