By Marcello Cherchi, MD PhD
For patients
Devices that use electricity generate a magnetic field. The very strong magnetic field of an MRI scanner can make the eyes jump (nystagmus) and make a person feel dizzy. The very weak magnetic field generated by small devices (such as a cellular telephone or a Bluetooth device) seem not to cause any hearing or balance problems.
For clinicians
Overview
When patients ask about the possible effects of “electromagnetic fields” on their health, they are usually asking about magnetic fields generated by MRI scanners, electrical power lines, cellular telephones and Bluetooth devices. Very strong magnetic fields (such as those present in an MRI scanner) can induce a magneto-hydrodynamic force in the endolymph of the semicircular canals, causing deflection of the cupula with corresponding nystagmus. The much weaker magnetic fields generated by handheld devices do not appear to have any measurable effect on cochleo-vestibular function.
Introduction
Patients sometimes ask clinicians about the possible effects of “electromagnetic fields (EMFs),” and are usually referring either to the risks of using small devices (such as a cellular telephone or Bluetooth headset) or the risks of their home being near electrical power lines.
Although these inquiries regard “electro-magnetic fields,” and although electrical and magnetic phenomena are intimately related, the clinician should bear in mind that such questions really pertain to the magnetic fields generated by electrical devices. Magnetic fields influence the movement of electrons (i.e., electrical currents) and the orientation of atoms and compounds. Patients are generally not asking about electrical phenomena such as would occur in unintentional electrocution, or intentional treatment with transcranial direct current stimulation.
Pathophysiological mechanism
There are several mechanisms by which magnetic fields could influence biological systems. Glover and colleagues categorize these into induced electrical currents, magneto-hydrodynamics, and tissue magnetic susceptibility differences (Glover et al. 2007).
Very powerful magnetic fields, such as are used in MRI scanners, can generate a biologically meaningful Lorentz force that influences ionic currents in the endolymph of the labyrinth (Antunes et al. 2012). Such magneto-hydrodynamic force (Glover et al. 2007) in turn can exert actual physical force on the cupula of the semicircular canals. This is thought to be the mechanism by which MRI can induce nystagmus in normal individuals (Ward et al. 2017; Ward et al. 2014, 2015; Ward et al. 2018). The strength of the magnetic field generated by a clinical MRI scanner is on the order of 1 to 3 Tesla.
Devices such as cellular telephones generate much weaker magnetic fields, sometimes referred to as “ELF” (extremely low frequency) magnetic fields (Cook et al. 2006; Cook et al. 2002). Experimental studies failed to detect any nystagmus induced by such weak fields (Pau et al. 2005).
Most research on this topic concludes that there is no evidence of any cochleo-vestibular effects of the electromagnetic fields generated by cellular telephones (Balbani and Montovani 2008; Johansen 2004; Kleinlogel et al. 2008; Mandala et al. 2014). Skeptics cast doubt on the validity of such research, noting that some of the published studies were funded by the cellular telephone industry (Marino and Carrubba 2009).
References
Antunes A, Glover PM, Li Y, Mian OS, Day BL (2012) Magnetic field effects on the vestibular system: calculation of the pressure on the cupula due to ionic current-induced Lorentz force. Phys Med Biol 57: 4477-87. doi: 10.1088/0031-9155/57/14/4477
Balbani AP, Montovani JC (2008) Mobile phones: influence on auditory and vestibular systems. Braz J Otorhinolaryngol 74: 125-31. doi: 10.1016/s1808-8694(15)30762-x
Cook CM, Saucier DM, Thomas AW, Prato FS (2006) Exposure to ELF magnetic and ELF-modulated radiofrequency fields: the time course of physiological and cognitive effects observed in recent studies (2001-2005). Bioelectromagnetics 27: 613-27. doi: 10.1002/bem.20247
Cook CM, Thomas AW, Prato FS (2002) Human electrophysiological and cognitive effects of exposure to ELF magnetic and ELF modulated RF and microwave fields: a review of recent studies. Bioelectromagnetics 23: 144-57. doi: 10.1002/bem.107
Glover PM, Cavin I, Qian W, Bowtell R, Gowland PA (2007) Magnetic-field-induced vertigo: a theoretical and experimental investigation. Bioelectromagnetics 28: 349-61. doi: 10.1002/bem.20316
Johansen C (2004) Electromagnetic fields and health effects–epidemiologic studies of cancer, diseases of the central nervous system and arrhythmia-related heart disease. Scand J Work Environ Health 30 Suppl 1: 1-30.
Kleinlogel H, Dierks T, Koenig T, Lehmann H, Minder A, Berz R (2008) Effects of weak mobile phone – electromagnetic fields (GSM, UMTS) on event related potentials and cognitive functions. Bioelectromagnetics 29: 488-97. doi: 10.1002/bem.20418
Mandala M, Colletti V, Sacchetto L, Manganotti P, Ramat S, Marcocci A, Colletti L (2014) Effect of Bluetooth headset and mobile phone electromagnetic fields on the human auditory nerve. Laryngoscope 124: 255-9. doi: 10.1002/lary.24103
Marino AA, Carrubba S (2009) The effects of mobile-phone electromagnetic fields on brain electrical activity: a critical analysis of the literature. Electromagn Biol Med 28: 250-74. doi: 10.3109/15368370902918912
Pau HW, Sievert U, Eggert S, Wild W (2005) Can electromagnetic fields emitted by mobile phones stimulate the vestibular organ? Otolaryngol Head Neck Surg 132: 43-9. doi: 10.1016/j.otohns.2004.09.008
Ward BK, Otero-Millan J, Jareonsettasin P, Schubert MC, Roberts DC, Zee DS (2017) Magnetic Vestibular Stimulation (MVS) As a Technique for Understanding the Normal and Diseased Labyrinth. Front Neurol 8: 122. doi: 10.3389/fneur.2017.00122
Ward BK, Roberts DC, Della Santina CC, Carey JP, Zee DS (2014) Magnetic vestibular stimulation in subjects with unilateral labyrinthine disorders. Front Neurol 5: 28. doi: 10.3389/fneur.2014.00028
Ward BK, Roberts DC, Della Santina CC, Carey JP, Zee DS (2015) Vestibular stimulation by magnetic fields. Ann N Y Acad Sci 1343: 69-79. doi: 10.1111/nyas.12702
Ward BK, Zee DS, Roberts DC, Schubert MC, Perez-Fernandez N, Otero-Millan J (2018) Visual Fixation and Continuous Head Rotations Have Minimal Effect on Set-Point Adaptation to Magnetic Vestibular Stimulation. Front Neurol 9: 1197. doi: 10.3389/fneur.2018.01197
