Epilepsia, 53(6):947–961, 2012
CRITICAL REVIEW AND INVITED COMMENTARY
Music and epilepsy: A critical review Melissa Jane Maguire
Department of Neurology, Leeds General Infirmary, Leeds, United Kingdom
The effect of music on patients with epileptic seizures is complex and at present poorly understood. Clinical stud- ies suggest that the processing of music within the human brain involves numerous cortical areas, extending beyond Heschl’s gyrus and working within connected networks. These networks could be recruited during a seizure mani- festing as musical phenomena. Similarly, if certain areas within the network are hyperexcitable, then there is a potential that particular sounds or certain music could act as epileptogenic triggers. This occurs in the case of musi- cogenic epilepsy, whereby seizures are triggered by music. Although it appears that this condition is rare, the exact prevalence is unknown, as often patients do not implicate music as an epileptogenic trigger and routine electroencephalography does not use sound in seizure provocation. Music therapy for refractory epilepsy remains controversial, and further research is needed to explore the potential anticonvulsant role of music. Dopa-
Music is an integral part of everyday life and culture. For most people, listening or playing music is a pleasurable experience that may evoke a memory or emotion. Advances in technology have improved our access to all kinds of music, with many people now downloading and sharing digitized music files and using portable devices to play and store large collections of music.
Although the environmental link between photosensitivity and epilepsy is well known, the interaction between music and epilepsy is less well perceived or understood. It appears some patients with seizures might gain benefit from musical exposure, whereas other patients may experience an exacer- bation of their seizures. The dichotomous effect of music on epilepsy is an intriguing yet poorly understood phenomenon and the subject of ongoing research and debate. In addition, the effects of medications and surgical procedures used in
Accepted April 3, 2012; Early View publication March 21, 2012.
Address correspondence to Melissa Maguire, Consultant Neurologist, Leeds General Infirmary, Great George Street, Leeds, West Yorkshire LS1 3EX, U.K. E-mail: email@example.com
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a 2012 International League Against Epilepsy
minergic system modulation and the ambivalent action of cognitive and sensory input in ictogenesis may provide possible theories for the dichotomous proconvulsant and anticonvulsant role of music in epilepsy. The effect of antiepileptic drugs and surgery on musicality should not be underestimated. Altered pitch perception in relation to carbamazepine is rare, but health care professionals should discuss this risk or consider alternative medication particularly if the patient is a professional musician or native-born Japanese. Studies observing the effect of epi- lepsy surgery on musicality suggest a risk with right tem- poral lobectomy, although the extent of this risk and correlation to size and area of resection need further delineation. This potential risk may bring into question whether tests on musical perception and memory should form part of the preoperative neuropsychological workup for patients embarking on surgery, particularly that of the right temporal lobe.
KEY WORDS: Musicogenic, Therapy, Carbamazepine, Temporal lobectomy.
epilepsy may have the potential to alter a patient’s musical- ity, which could have disastrous consequences.
This review aims to summarize the current body of evi- dence on music and its association with epilepsy. It outlines our current understanding of musical processing in the human brain, and how this process could be disrupted in the production and propagation of seizures. Also discussed are ictal musical phenomena, music therapy in refractory epi- lepsy, and the effect of antiepileptic medication and epi- lepsy surgery on musicality.
Musical Processing and the Human Brain
The relation between music and the brain has been exten- sively researched over the past century, from the authorita- tive work published by Critchley and Henson (1977) titled ‘‘Music and the Brain’’ to a modern update of the literature from intervening decades by Stewart et al. (2006).
During the late 19th century, German researchers pub- lished numerous studies analyzing the disturbance of musical functioning in patients with brain damage, observing how focal lesions affect musical activities. In 1888, Knoblauch
M. J. Maguire
introduced the term ‘‘amusia’’ meaning impaired musical capabilities. He described a sensory (receptive) amusia whereby affected patients cannot hear, read, or understand music, and motor (expressive) amusia whereby patients have an inability to sing, write, or play music (Knoblauch, 1888). Several other authors explored lesional conse- quences on music perception (Head, 1926; Kleist, 1962; Luria et al., 1965), and a plethora of interesting discoveries were made. Although many cases of amusia were related to an abnormality within the right temporal lobe, this was by no means true in all reported cases and some lesions lateral- ized to the left hemisphere. Thalamic lesions in association with a hemiparesis were reported to cause a peculiar alter- ation in musical perception on the affected side. One patient seemed unable to tolerate hymns in church on his affected side, causing him to rub the affected hand (Head, 1920). Although these studies provided some evidence on the ana- tomic components of musical perception, the cases were confined to patients with damaged brains, and it is possible that the underlying pathologic process may have affected the results.
Our modern understanding of the mechanisms involved in musical processing has been aided by advances in func- tional imaging studies, using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) techniques. These techniques display the changes in hemo- dynamic response to mean synaptic firing rates in the brain, and have allowed researchers to delineate the anatomic areas pertinent to the processing of music. Electroencepha- lography (EEG) and magnetoencephalography (MEG) stud- ies have also been employed to record postsynaptic potentials during listening to music. Recent studies have also identified the structural and functional organization of the brain in musicians.
Musical processing encompasses brain mechanisms in musical perception, recognition, and emotion. Musical per- ception requires the decoding of a musical stimulus within the primary auditory cortex in Heschl’s gyrus and the associ- ation cortex in the superior temporal gyrus (planum tempo- rale). The primary auditory cortex is thought to receive thalamic afferents from the medial geniculate nucleus, which in turn connect through networks to the association cortex, mesolimbic systems, and other multisensory cortices (Stewart et al., 2006). The primary auditory cortex appears especially sensitive to tone, whereas the auditory associa- tion cortex is thought to perceive pitch (Penagos et al., 2004) and perform more complex musical processing tasks relating to linear stimuli, for example, melodies (Liegeois- Chauvel et al., 1998) and nonlinear stimuli, for example, chords and consonances. Similar areas within the secondary auditory cortex are also activated in speech (Price et al., 2005). The perception of rhythms, with no particular melo- dic content, is thought to involve activation of the cerebel- lum and basal ganglia as well as the superior temporal lobes, suggesting a motor aspect to rhythm perception.
Epilepsia, 53(6):947–961, 2012
Musical recognition and emotion are thought to involve orbitofrontal areas and the limbic system, which may serve to store past auditory memory and emotional evalu- ation of a musical stimulus (Dellacherie et al., 2009). For example, chord dissonance per se may be detected via the auditory association cortex, but the evoked unpleasant emotional response appears to be mediated via limbic structures.
An extensive review by Stewart et al. (2006)) analyzed 38 case reports and 27 case series reporting on symptom- atic musical listening deficits, with associated structural imaging findings. The authors summarized anatomic areas that are pertinent to pitch processing, temporal processing, musical memory, and emotional responses to music using five cartoons. Anatomic areas implicated in 50% or more of the studies for a particular function were mapped out using colored dots, with the size of the dot representing the proportion of studies (Fig. 1). The review ascertained that the anatomic areas implicated in musical listening deficits were central, affecting a number of regions beyond Heschl’s gyrus, with right-sided predominance. Half of cases were associated with coexisting problems of speech perception.
Determinants of musicality have also been explored over the years by examining environmental and genetic factors. Musicality is likely to be a polygenic trait and dependent on home environment and parental attitudes to the develop- ment of musical talent in children.
Studies have also identified structural differences in the brains of musicians versus nonmusicians in a number of anatomic areas including auditory (Schneider et al., 2002), motor (Amunts et al., 1997), somatosensory, supe- rior parietal (Gaser & Schlaug, 2003), callosal (Schlaug et al., 1995), and cerebellar (Hutchinson et al., 2003) areas. The larger size of the corpus callosum in musicians may indicate increased cross-communication between both sides of the brain, merging spatial-emotional process- ing of the right brain with linguistic analytical processing of the left brain. People with absolute pitch engage left dorsofrontal regions, whereas those lacking absolute pitch appear to have a so-called working memory for pitch located within inferior frontal areas. The age of onset of musical training, that is, younger than 4 years old, appears to be a key predictor of absolute pitch, suggesting that this ability develops during a critical period for imprinting (Sergeant & Roche, 1973).
Music and Epilepsy
It is possible that brain mechanisms involved in musical processing may be involved in the generation and propaga- tion of seizures, manifesting with musical semiology. Hyperexcitable cortical areas may also become sensitized to specific musical triggers and may explain the basis of musicogenic epilepsy.