Muscle ischaemia in patients with orthostatic hypotension assessed by velocity recovery cycles

• Published in: Journal of neurology, neurosurgery and psychiatry Vol. 82; no. 12; pp. 1394 - 1398
• Main Authors: Humm, Andrea Monika, Bostock, Hugh, Troller, Rebekka, Z'Graggen, Werner Josef
• Format: Journal Article
• Language: English
• Published: London BMJ Publishing Group Ltd 01.12.2011; BMJ Publishing Group; BMJ Publishing Group LTD
• Subjects: Action Potentials - physiology; Adult; Aged; Aged, 80 and over; Biological and medical sciences; Case-Control Studies; clinical; Electrodes; Fainting; Female; Hemodynamics; Humans; Hypotension, Orthostatic - complications; Hypotension, Orthostatic - physiopathology; ischaemia; Ischemia; Ischemia - complications; Ischemia - physiopathology; Male; Medical sciences; Middle Aged; Multiple sclerosis and variants. Guillain barré syndrome and other inflammatory polyneuropathies. Leukoencephalitis; multiple system atrophy; Multiple System Atrophy - complications; Multiple System Atrophy - physiopathology; muscle membrane potential; muscle pain; Muscle velocity recovery cycle; Muscle, Skeletal - physiopathology; myopathy; Neck Pain - complications; Neck Pain - physiopathology; Neurology; neurophysiol; neurophysiology; Orthostatic hypotension; Parkinson's disease; peripheral neuropathology; Potassium; Tilt-Table Test - methods; Tilt-Table Test - statistics & numerical data; United Kingdom > UK; United States > US; Human; Postural hypotension; Nervous system diseases; Ischemia; Arterial hypotension; Diseases of the autonomic nervous system; Cardiovascular disease; Recovery
• DOI: 10.1136/jnnp-2011-300444
• ISSN: 0022-3050

ObjectivePatients with orthostatic hypotension may experience neck pain radiating to the occipital region of the skull and the shoulders while standing (so-called coat-hanger ache). This study assessed muscle membrane potential in the trapezius muscle of patients with orthostatic hypotension and healthy subjects during head-up tilt (HUT), by measuring velocity recovery cycles (VRCs) of muscle action potentials as an indicator of muscle membrane potential.MethodsEight patients with multiple system atrophy (MSA), orthostatic hypotension and a positive history for coat-hanger pain and eight normal controls (NCs) were included in this study. Repeated VRCs were recorded from the trapezius muscle by direct muscle stimulation in the supine position and during HUT for 10 min.ResultsMuscle VRC recordings did not differ between MSA patients and NCs in the supine position. During HUT, early supernormality decreased progressively and relative refractory period increased in MSA patients whereas VRC measures remained unchanged in NCs. Ten minutes after the start of HUT, early supernormality was reduced by 44% and relative refractory period was increased by 17%.ConclusionsMuscle membranes in patients with orthostatic hypotension become progressively depolarised during standing. Membrane depolarisation is most likely the result of muscle ischaemia, related to the drop in perfusion pressure caused by orthostatic hypotension. Coat-hanger ache is most likely a consequence of this muscle ischaemia.