Palinacousis: an eloquent symptom of temporal lobe lesion
- Catherine Veilleux ,
- Gilles El-Hage ,
- Nathalie L'Ecuyer and
- Michel W Bojanowski
- Division of Neurosurgery, University of Montreal, Montreal, Quebec, Canada
- Correspondence to Professor Michel W Bojanowski, Division of Neurosurgery, University of Montreal, Montreal, Quebec, Canada; michel.bojanowski.chum@ssss.gouv.qc.ca
Abstract
A 24-year-old woman was referred to us for an intracranial haemorrhage in the left temporal lobe caused by a ruptured cavernous malformation; the bleeding extended over the left Heschl’s gyrus and Wernicke area. On admission, the patient had global aphasia. A few days later, she spontaneously improved but remained with mild residual comprehensive dysphasia. She reported hearing, in her right ear, recently heard words, which is consistent with palinacousis. Auditory acuity testing was normal. EEG showed focal slowing in the left temporal region with no epileptiform activity. During awake surgery for resection of the cavernous malformation, stimulation of the superior temporal gyrus did not provoke palinacousis. The patient made good recovery with complete resolution of the aphasia and no recurrence of palinacousis. We aimed to review this phenomenon and to provide a systematic review of the current literature.
Background
Palinacousis was first described in 1971 by Jacobs et al 1 as a perseveration or recurrence of recent auditory sensations after the stimulus has ceased. This phenomenon was first observed intraoperatively during temporal lobe stimulation by Wilder Penfield,2 which he reported in 1963, but the term ‘palinacousis’ was later coined by Jacobs et al.1 Such episodes of hearing usually last from seconds to hours.3 Hence, unlike auditory phenomena in many psychiatric conditions, the sounds perceived in palinacousis are not persecutory delusions. In palinacousis, the auditory sensations may include spoken language, vocal sounds, musical sounds as well as environmental sounds.4–6 Although it has been hypothesised that palinacousis may be caused by seizures, its pathophysiology is still poorly understood.3
We report the case of a patient who experienced palinacousis following a brain haemorrhage in the Heschl’s gyrus and in the Wernicke area due to a ruptured cavernous malformation (CM). Paraclinical evaluation did not reveal evidence of seizure activity. Likewise, intraoperative cortical stimulation did not induce palinacousis.
Our goal in reporting a case of palinacousis and systematically reviewing the literature regarding this rare condition is to highlight the fact that palinacousis is almost always associated with a recognisable structural brain lesion and that care must be taken so as to not confuse it with other forms of auditory hallucinations. We will also discuss possible mechanisms involved in its pathophysiology.
Case presentation
A 24-year-old Caucasian right-handed woman was transferred to our hospital for global aphasia of unknown aetiology. She had no neurological or psychiatric history and had completed undergraduate studies. MRI revealed left-sided subarachnoid haemorrhage and intraparenchymal haemorrhage in the left temporal lobe, involving the Heschl’s gyrus and the Wernicke area, secondary to a ruptured CM. Significant oedema of the surrounding brain tissue was also present (figure 1). Three days later, as her aphasic symptoms greatly diminished, the patient reported hearing previous recently heard words and sounds in her right ear. Most of the time, she heard only one word, although she reported hearing paraphrases at times. She reported these spontaneous repetitions of past sounds to be more frequent before bedtime or during a conversation. The maximal delay between the stimulus and the echo was 1 hour, and she usually heard the echo immediately following cessation of the stimulus. These auditory hallucinations were vivid and she was fully aware of them. The episodes lasted from 30 s to 5 min. She described the sound as a neutral voice, which might have been her own, and was uncertain whether she would be able to determine the gender of the voice. Although she was unable to stop the reoccurrence of these echoes, she was still capable of focusing her attention on the current conversations she was having with her left ear. However, it did at times disrupt the conversation, as she was under the impression people were conversing using the same words over and over again, making it difficult to follow. She did not have any other symptoms including emotional disturbance or signs of psychiatric illness. She did, however, present residual deficits in word association, word recognition and word-finding at the time of her palinacousis. Palinacousis disappeared spontaneously within approximately 48 hours of its emergence.
T2 Fast Fluid Attenuated Inversion Recovery (FLAIR) Coronal and Axial MRI demonstrating the cavernous malformation extending over the left gyrus of Heschl.
Investigations
Head MRI revealed a left temporal parenchymal haematoma with oedema extending over the Heschl’s gyrus and Wernicke area due to the rupture of a CM (figure 1). An adjacent venous developmental anomaly draining into the left lateral ventricle was also noted. These findings were consistent with the underlying ruptured cavernoma.
Speech assessment was done 48 hours after her admission and revealed mild to moderate receptive aphasia with impaired oral and written comprehension as well as impaired verbal memory. A mild difficulty pronouncing and repeating words was also noted. Speech was fluent, with adequate content using complex sentences.
An electroencephalogram (EEG) was conducted a few days after the symptoms had ceased and showed focal slowing in the left temporal region with no epileptiform abnormalities. Auditory acuity testing was within normal limits.
Treatment
In order to avoid a rebleeding of the CM, surgical resection was proposed. Nine days following admission, awake brain surgery was undertaken. To prevent seizure during the surgery, a bolus of phenytoin was administered prior to surgery. During the surgery, cortical stimulation of the superior temporal gyrus was performed, and the stimulations did not reproduce any palinacousis. The haematoma was suctioned out, followed by resection of the cavernoma while preserving the associated venous developmental anomaly (video 1). The surgery was uneventful.
Outcome and follow-up
Postoperatively, the patient had no new neurological deficit. She was discharged 4 days following surgery and levetiracetam was prescribed prophylactically for a period of 2 months given that there had been a ruptured symptomatic CM for which the patient had undergone surgery and that palinacousis may have been a seizure phenomenon. Two months later, when the patient was seen in the outpatient clinic, neurological examination was normal and there was no recurrence of the palinacousis. MRI revealed no residual CM (figure 2). The patient was seen again 6 months following surgery and was symptom-free.
T2 Fast Fluid Attenuated Inversion (FLAIR) Coronal and Axial MRI demonstrating postoperative status and complete resection of the cavernous malformation.
Discussion
Palinacousis is an auditory perception of previously heard sounds occurring after the corresponding external auditory stimulus has ceased. It is distinct from the types of auditory hallucinations experienced in psychiatric disorders such as schizophrenia or mood disorders, as there are no paranoid thoughts nor are the sounds emotionally upsetting. Furthermore, there are no other neurotic or psychotic symptoms nor history thereof in palinacousis. Palinacousis is further triggered by an auditory stimulus, whereas auditory hallucinations in psychotic illnesses are not. These differences are important in order to avoid misdiagnosing palinacousis as a mental illness.3 In palinacousis, the patient is fully aware that the sound is an echo of a previously heard sound, and there is no irrational affective response. Pseudo-hallucinations also present with preserved insight in the absence of psychotic symptoms, as in our patient’s case; however, they are typically described as ‘not as vivid’ as true hallucinations, which was not the case in our patient.7 Furthermore, pseudo-hallucinations often involve more than one sensory modality and have a ‘naïve, fantastic or childish content’, which again was not the case in our patient.8
We conducted a systematic review following the guidelines of the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols. A PubMed search of the word ‘palinacousis’ yielded 26 reports, including 3 review articles. All articles were cross-referenced to look for other case reports or case series of palinacousis in human subjects. All publications were considered and there were no exclusions based on year of publication or primary language of the article. Articles were excluded if the reported case did not describe perseveration of previously heard sounds or words. We also excluded all review articles of palinacousis (online supplemental figure E1).3 4 6 9 Consequently, we retained in our systematic review 22 articles for a total of 35 cases,1 4 6–25 to which we added our own case for a total of 36 cases in this study. A detailed description and flow chart of all identified cases can be found in online supplemental table E1 and figure E1.
Supplementary data
Supplementary data
Palinacousis may occur at any age; in the cases described, ages ranged between 15 and 78 years. Men and women also appear to be equally affected (table 1). In cases where handedness was reported, there were no left-handed patients, while 10 were right-handed,11 13 14 17 23 24 26 27 including our patient (table 2). Most patients heard the perseverating sound immediately after cessation of the original auditory stimulus.1 10 11 14 15 17 18 23 27 Some cases report patients heard their own voice as an echo.5 10 13 14 17 21 28 Some patients also reported perseveration of their inner speech,10 14 22 which has been termed palinendophonia by a group of authors.14 In cases where speech deficits or absence thereof was reported, six patients had no speech deficits,10 13 22 23 six had receptive aphasia,11 15–17 19 including our case, one was globally aphasic,17 28 while one had non-specific speech abnormalities.16 Palinopsia, which is defined as perseveration or recurrence of a visual image after the stimulus has ceased, was also described concurrently with palinacousis in four cases.6 24 25
Demographic characteristics
| Subject group | Frequency (%) or mean±SD |
| Age (years) | 46.7±19.3 |
| Male | 47.2 |
| Female | 50.0 |
| Non-specified sex | 2.8 |
Clinical presentation characteristics
| Subject group | Cases, n (frequency %) |
| Lesion aetiology | |
| Tumour (glioblastoma, meningioma, metastases, schwannoma unspecified brain tumour) | 8 (22.2) |
| Vascular malformation | 4 (11.1) |
| Intraparenchymal haemorrhage | 4 (11.1) |
| Postoperative changes | 2 (5.6) |
| Others (polymicrogyria, temporal epilepsy, infarction, Wernicke encephalopathy, hypoperfusion, necrosis, etc) | 9 (22.2) |
| Non-lesional | 5 (13.9) |
| Non-specified | 5 (13.9) |
| Handedness | |
| Right-handed | 10 (27.8) |
| Left-handed | 0 (0) |
| Ambidextrous | 1 (2.8) |
| Non-specified | 25 (69.4) |
| Lesion lateralisation | |
| Right hemisphere | 14 (38.9) |
| Left hemisphere | 14 (38.9) |
| Bilateral | 3 (8.3) |
| Others (ie, alcohol cessation, antipsychotic cessation) | 5 (13.9) |
| Lobe localisation | |
| Temporal | 14 (38.9) |
| Frontotemporal | 4 (11.1) |
| Temporo-occipital | 4 (11.1) |
| Parietal | 3 (8.3) |
| Temporoparietal | 3 (8.3) |
| Others (ie, inferior colliculi, medial geniculate nucleus) | 3 (8.3) |
| Non-applicable (ie, alcohol cessation, antipsychotic cessation) | 5 (13.9) |
The aetiology of lesions responsible for palinacousis is diverse, but almost all are located in the temporal lobe,1 10 12 15 16 21 29 often in the superior temporal gyrus in proximity to or at the primary auditory area (transverse gyrus of Heschl). The most common lesions found are cerebral tumours, both intra-axial and extra-axial including glioblastoma (n=4),10 24 26 28 metastases (n=2),15 16 meningioma (n=2)1 17 and schwannoma (n=1).1 Other aetiologies include vascular malformations such as CMs (n=2),17 as in our own case, arteriovenous malformation (n=1) or capillary venous malformation (n=1),10 as well as intraparenchymal haemorrhage,10 13 19 27 postoperative complications10 17 or ischaemic infarct.23 When specified, lesions were lateralised equally in the dominant and non-dominant hemispheres.1 7 11 12 14–18 20–22 24 25 Five cases appeared to be non-lesional, including cases such as alcohol20 or antipsychotic withdrawal,18 epileptic seizures,25 as well as cases in which no lesion was seen on imaging.1 21 However, in cases where palinacousis was lesional, the echo of the auditory stimulus was heard, most of the time, in the contralateral ear,1 10 12 17 24 26 28 although it was sometimes heard bilaterally,5 14 or in some cases the patient was not able to distinguish which ear was perceiving the sound.10 15 17 27 One exception was a case of an infarct of the right medial geniculate nucleus (MGN) in which the patient reported hearing the echoed sounds exclusively in his right ear, thus ipsilaterally to the lesion.23
The pathophysiology of palinacousis has been debated. It has been hypothesised to be associated with seizure phenomena1 3 11 12 17 21 22 24 26–28 and thought to occur secondary to a hyperexcitability of the auditory cortex. Penfield and Perot,2 using electrical brain stimulation during awake surgery, were able to provoke auditory hallucinations of sounds which had been heard in the remote past. This response occurred only when the stimulus was applied to the temporal cortex. In our case, we were unable to reproduce palinacousis when applying electrical stimulation during surgery, perhaps due to the presence of anticonvulsive medication, although we believe this is unlikely because the intensity of stimulation reached a high enough level to elicit a response despite anticonvulsive medication. It is interesting to note that our review of the palinacousis shows EEGs were normal in 22% of cases,10–14 18 22 25 and an additional 19.5% of cases only showed localised slowing with no epileptiform abnormalities.15 16 19 24 26–28 One could argue that EEG was negative in our case because it was not conducted while our patient was experiencing her symptoms. However, previous studies showing EEGs conducted while patients were experiencing palinacousis revealed no epileptiform abnormalities.13 16 Therefore, it remains unclear whether this truly represents a phenomenon related to seizures.
It has also been postulated that palinacousis may be a postictal loss of normal suppression of auditory perseveration.16 This negative release mechanism may not necessarily follow an ictal discharge. The authors from this study conducted a fluorodeoxyglucose-positron emission tomography (FDG-PET) while their patient was experiencing palinacousis, which showed hypometabolism, hence favouring a non-ictal hypothesis,16 or at least that a hypothesis in which a loss of function of one of the components of the auditory pathway is more plausible.
In normal hearing, when an external sound is perceived, the vibration is transformed in the ear into an electrical signal which is then transmitted via the cochlear nerve for subcortical processing. The cochlear nuclei in the brainstem send the impulse to the inferior colliculus bilaterally, although with a contralateral preponderance.30 From the inferior colliculi, it travels to the MGNs of the thalami, which then transmit the impulse to the primary auditory cortex on their respective sides. Of course, during its transit along the connecting fibres, the impulse is extensively processed. Since stimulated neurons convey overlapping information, Chechik et al 31 have postulated that one of the processing functions is to reduce the amount of redundant auditory information. They showed that the MGN and the auditory cortex play a significant role in suppressing informational redundancy. Thus, we can hypothesise that the auditory cortex plays a role in suppressing redundant information mainly contralaterally, at least in most individuals. However, in one report, an isolated lesion in the MGN produced palinacousis ipsilateral to the lesion.23 This is rather interesting, as Hugdahl et al 32 had previously reported the case of a patient performing above average in detecting sounds ipsilaterally to a right pulvinar lesion. Based on these observations, it would appear that palinacousis may be related to a network dysfunction rather than to the effect of a local lesion. This may explain why if intraoperative electrical stimulation were applied after network reorganisation it may not reproduce palinacousis.
Palinacousis remains a rare phenomenon that can be seen in patients with lesions such as tumours and intraparenchymal haemorrhages, which are mainly located in the temporal lobe, near the gyrus of Heschl, as was the case in our patient. These manifestations must be differentiated from psychiatric auditory hallucinations, as removal of the lesion tends to lead to a resolution of the symptoms. Auditory pathways are not fully understood by neuroscientists to this day, and a better understanding of the laterality of both ascending and descending pathways will allow us to better understand the pathophysiology behind palinacousis.
Patient’s perspective
It all started as I was trying to meet friends downtown, and as I was texting them, I could not seem to be able to press on the “Enter” button on my phone. That is when I noticed I could not see half of my screen. In fact, half of my visual field was missing. I believe it was the right hemifield. I then went inside a museum to ask for help, but I was unable to speak. I tried to show them my phone, and ask for help, but I don’t think they were able to understand me. I further called a relative, who was able to tell something was abnormal. The friends I was supposed to meet were able to find me with the iPhone app “Find my Friends”. They called for help. I remember the arrival of EMS at the museum, but lost consciousness until I was transferred to a university hospital. I was first brought to another regional hospital. Although I don’t remember it myself, I was told that doctors thought I had been drugged and ran many toxicologic screens until they found the bleed in my brain and sent me to the teaching hospital.
I regained consciousness at the hospital. My vision was then completely normal. My recollection of the first few days I spent in the hospital is rather blurry. I remember that doctors and nurses would come in to ask me the usual questions, including my name, the date, and where I was. I was unable to say my own name, and would mostly say yes to all questions, including my name! They did a thorough neurological examination, and I remember being able to perform mathematical calculations. The palinacousis started on the first night I spent at the teaching hospital. My friends and relatives were speaking, and as we would all be having a conversation, I would hear one or two words they had said over and over in my right ear. I was able to keep conversing because my left ear allowed me to do so. I first thought something was wrong with my right ear apparatus. It never crossed my mind that I was hallucinating, and I was not too worried, because I have ophthalmic migraines, so I don’t panic with weird neurological phenomenon anymore. What I think worried me is when I told my neurosurgeon about it, and he said he would look into it because he had never seen that before. That had me more worried than anything, but he came back with an answer the next day, which reassured me.
During the first few days in the hospital, I also experienced memory problems. As I regained the ability to speak and understand what I was asked to do or say, I could not recall simple information nor information that should have been easy for me, such as my home address. I also did not quite understand why they were keeping me in the hospital. I was supposed to go see a relative by plane that week and remember thinking I was doing better and as such, kept on asking to leave the hospital to go on that trip. Four days after I was admitted to the university hospital, as my language was improving, the neurosurgery team met with my family and I. The lead surgeon showed us the images and explained that I had bled in my brain due to a malformation of vessels. It then became pretty clear why I was in the hospital. I felt very calm as he explained everything and described the operation he would be performing. My parents asked many questions, but I felt very confident.
About a week later, I underwent awake surgery for electrical stimulation and removal of my malformation. I don’t think I had really measured the magnitude of this operation until after I underwent it when a nurse said I was courageous for accepting to undergo brain surgery – completely awake! Everything went smoothly during the surgery. My neurosurgeon would sometimes ask me questions or get me to speak. I felt calm and confident during the surgery - I knew I was in good hands. They said they would freeze the scalp, and give me sedation during the surgery, and I was told I could “ask for freeze” if I felt some pulling or pain. I “asked for freeze” twice during the surgery but I have no recollection of pain during the surgery. A nurse was with me the whole time. I remember being able to answer questions, but I must say the details of the surgery are quite blurry.
Postoperatively, I improved quickly. I saw a speech therapist in the hospital, who said I was improving, although I still had mild deficits at the time. She offered her services as an outpatient, but I thought I improved quickly thereafter. I could still notice it at first, as I would be looking for words. I remember thinking my vocabulary was not as good as it used to be when I was in university, but my friends reassured me they could not notice it. I still had a few problems with my memory postoperatively. For instance, I had traveled through Europe for a few months with a friend prior to my brain bleed, and I could not remember anything about that trip. My friend recounted me our trip, and as she would tell our stories, the memories would come back. Furthermore, for about a month after I left the hospital, I would have nightmares where half my brain would bleed out, and when I woke up from these nightmares, I would have a taste of blood in my mouth. We are now a year from my awake brain surgery, and I still can’t believe how calm I was through this episode of my life. I am doing great now – I don’t have any nightmares, and both my language and memory are back to normal. I am back to living a pretty normal life!
Learning points
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Palinacousis is a perseveration of previously heard sounds distinct from psychiatric auditory hallucinations.
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It is highly suggestive of a brain lesion, most often in the temporal lobe.
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When suspected, brain imaging is required.
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The mechanism is debated but may be ictal, postictal or non-ictal.
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Recognition may allow for earlier treatment of the cause (tumour, brain haemorrhage, postoperative complication and so on).
Footnotes
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Contributors CV: took the lead in writing the manuscript, conducted review of current literature, prepared figures 1 and 2, conducted the interview for patient’s perspective. GE-H: contributed to video preparation, assumed critical revision of the manuscript for intellectual content. NL’E: contributed to conducting the interview for patient's perspective, assumed critical revision of the manuscript for intellectual content, gathered patient’s data for case report. MWB: original idea, assumed critical revision of the manuscript for intellectual content, lead neurosurgeon on the case.
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Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
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Competing interests None declared.
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Provenance and peer review Not commissioned; externally peer reviewed.
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