Dizziness can be protean with multiple phenotypes. One common phenotype in the young population is postural orthostatic tachycardia syndrome (POTS). POTS has a unique cardiovascular signature with a fascinating range of etiologies and pharmacodynamic substrates. This condition can pass undiagnosed for many years and is often mistaken as an anxiety disorder due to some of its hyperadrenergic manifestations. We present one such case and then flesh out the treatment strategies, both conservative and pharmacologic. We finally describe the various underlying pathophysiologic mechanisms of POTS and its sub-types and outline the various aberrant cardiovascular reflexes. We also describe the power spectra of the heart rate variability frequency bands and their underlying physiologic basis.
Immune-mediated necrotizing myopathy (IMNM) is a rare idiopathic disease that is further classified by the presence of serum antibodies. A modicum of patients lack serum autoantibodies. Significantly elevated creatine kinase (CK) is highly characteristic of IMNM. The pathophysiology of IMNM is partially understood, and effective treatment options are limited, particularly in patients without serum autoantibodies. In this case, we report a 76year-old male presenting with a four-month history of proximal muscle weakness. Muscle biopsy and serology confirmed the diagnosis of autoantibody-negative IMNM. Early and aggressive treatment with high-dose steroids and a course of intravenous immunoglobulin significantly reduced the patient's symptoms and CK within three months. This case serves as an example of an effective treatment outcome in a patient with this rare idiopathic necrotizing myopathy.
Meralgia paresthetica, a condition characterized by tingling, numbness, and burning pain in the lateral aspect of the thigh, is caused by compression of the lateral femoral cutaneous nerve. The incidence of meralgia paresthetica increases with obesity and diabetes. The unique anatomy of the nerve that tunnels through the inguinal ligament predisposes it to inflammation, trauma, and entrapment. The pathology of meralgia paresthetica parallels that of entrapment neuropathies but with additional inflammatory overlay in certain instances. The clinical diagnosis is relatively simple due to its unique clinical features. The prognosis is generally excellent, and the treatment is straightforward that includes peripheral nerve blocks, neurectomy, nerve decompression, and pulsed radiofrequency neuromodulation. This current case of meralgia paresthetica highlights the salient clinical symptoms and signs. We have also described the electrophysiological studies of the lateral femoral cutaneous nerve, its anatomical variations, and the associations of meralgia paresthetica with bariatric surgery, critical care patients, tight clothing, pregnancy, and posterior spine surgery. We have also outlined the current treatment strategies.
Recent data from astronauts who have returned to Earth from a long-duration space flight have unequivocally distinguished spaceflight-associated neuro-ocular syndrome (SANS) from idiopathic intracranial hypertension (IIH) and pseudotumor cerebri (PTC). We review the semiology and pathogenesis of these three entities, noting that optic disc edema is what unites them, and this where the similarities between SANS and IIH/PTC end. We distinguish between PTC and IIH and between SANS and IIH/PTC and review the medical and surgical therapy of IIH/PTC. The key to understanding the phenomenon of optic disc edema is the geometry of the optic nerve sheath, which is a simulacrum of an inverted Venturi tube. This allows us to theoretically study the hydrodynamics of the optic nerve sheath by applying simple physical laws, including the Venturi effect, Poiseuille's law, and Reynold's number, and we speculate on nature's design and the correlation of form and function in understanding how cerebrospinal fluid (CSF) circulates in the optic nerve sheath as it approaches the optic nerve head. Recent spectacular data on the histology of the blood nerve-barrier of the optic nerve disc and the glymphatic system of the optic nerve sheath will also help us understand the development of optic disc edema due to the microgravity-induced cephalad shift of CSF in SANS. We will explore the role of the sodium/potassium adenosine triphosphatase (ATPase) pump on choroid plexus epithelial cells and the aquaporin-4 water receptors located on astrocyte end-feet and their complex interactions with the tetracyclines, mineralocorticoids, and therapeutic agents with carbonic anhydrase activity. We also adumbrate the complex interactions between obesity, vitamin A, and 11-beta-hydroxysteroid dehydrogenase and how the aquaporin-4 receptor relates to these interactions.
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