This video shows a PD patient presenting string hallucinations during an outpatient visit. Along this visit, the patient start to scratch his fingers trying to remove something from them, and the doctor asks him about this curious behavior. The patient recognizes that he is having “string hallucinations” and he describes that he is feeling and seeing strings in his fingers that he is trying to take them out.
Jesús Pérez-Pérez MD, Javier Pagonabarraga MD, PhD, Ramón Fernández-Bobadilla PhD and Jaime Kulisevsky MD, PhD
Article first published online: 23 NOV 2015 | DOI: 10.1002/mdc3.12252
The aim of this work was to report on 7 patients presenting a distinctive form of multimodal (tactile and visual) hallucinations for which the term “string hallucinations” is proposed. Having observed a patient interacting with imaginary strips of skin in his hands at our movement disorders unit, we prospectively studied PD patients and caregivers over a 6-month period using a semistructured interview addressed to this particular phenomenon. Demographic characteristics as well as cognitive and motor function were assessed. A total of 7 of 164 PD patients (4.3%) observed during the study period had string hallucinations. One patient was cognitively intact and the other 6 had some degree of cognitive impairment. Common to the phenomenology of the hallucinations was the unpleasant feeling and vision of threads emerging from the subjects’ hands. Patients interacted with these “threads,” trying to remove them from their hands. Our study identifies a previously undescribed type of hallucinations in PD, characterized by a complex pattern of multimodal tactile and visual hallucinations.
Hallucinations are frequent in Parkinson's disease (PD) patients and mainly visual in nature. Reported to occur from early stages of the disorder, they increase in intensity and frequency as the disease progresses and are present in up to 70% of advanced patients, particularly in those with cognitive impairment.[1-3] Although patients rarely spontaneously report their existence, they can be distressful both for patients and caregivers, especially if they are not recognized as a phenomenon associated with PD.[1, 2, 4] Visual hallucinations are characteristic, but auditory, olfactory, and tactile hallucinations have also been described. Little attention has been given, however, to multisensory hallucinations that, if unrecognized as PD-associated phenomena, may be misinterpreted.[1, 2, 5]
Having observed a patient interacting with imaginary strips of skin in his hands, we interviewed outpatients and caregivers for the presence and characteristics of this curious behavior. We found this to be a distinctive and disturbing phenomenon, consistently described by our patients as the feeling and vision of threads or long strands of skin in, or around, their hands or emerging from their fingers. We here propose the term “string hallucinations,” which may help clinicians to recognize and treat them in any given patient.
Patients and Methods
Outpatients diagnosed with idiopathic PD attending our movement disorders unit from March to September 2013 (n = 164) were prospectively screened using a semistructured interview. We specifically asked whether they had ever seen and felt something in their skin that was not really there. Whether or not the patient presented cognitive impairment, we also asked caregivers—when available—the same question. We also recorded hallucination in other sensory modalities, as well as their duration, time of evolution, frequency, intensity, triggering factors (i.e., sleep disturbances), and daytime patterns. Sensory or other neurological disturbances were excluded using a comprehensive neurological assessment. Demographic and clinical data recorded included H & Y stage, current medication, eventual changes in therapy, and the course of hallucinations at follow-up visits. Cognitive performance was assessed using the Parkinson's Disease Cognitive Rating Scale (PD-CRS).[6, 7]
Informed consent to participate in the study was obtained from all participants, according to the Declaration of Helsinki.
A total of 7 of 164 (4.3%) PD patients screened fulfilled the inclusion criteria (3 women, 4 men; mean age: 81.4 ± 5 years).
Six of the seven patients had cognitive impairment (PD-MCI = 2; PD dementia = 4). The cognitively intact subject was 75 years old with only 3 years of PD (H&Y = 2). In contrast, the cognitively impaired group was older (82.5 ± 5 years) with long-duration and more advanced PD (14.3 ± 11 years; H & Y ≥ 3).
All patients were taking levodopa and 3 were also taking dopamine agonists. Table 1 summarizes the hallucination profile.
Table 1. Clinical characteristics of patients and hallucinations profile
||Disease Duration (Years)
||H & Y
||l-dopa dose (mg/day)
||DA Dose (mg/day)
||Duration of SH (Years)
Maximum score of 134; cutoff for mild cognitive impairment (MCI) ≤81 points and ≤64 for dementia.[9, 1
M, male; F, female; DA dose, dopaminergic agonist dose; SH, string hallucinations
||Tactile (touching) presence
||Formed visual, auditive
Phenomenology of the Hallucinations
The 7 patients had hallucinations that consisted of seeing and feeling long strands of skin or yarn coming out from their fingers. String hallucinations were present in both hands in all 7 patients. All patients complained of a strong urge to pull them out to relieve the annoying sensation. Three patients even gestured to wind the strands into a ball, which they then deposited on nearby furniture (see Video 1).
The mean time from disease onset to presentation of the string hallucinations was 5.7 ± 3.5 years. Patients were more likely to present these hallucinations in the evening, usually in states of sleepiness. In the cognitively intact patient, string hallucinations appeared only in the sleep-to-wake transition. Frequency of the hallucinations fluctuated in each patient and between patients, but they were more recurrent (weekly) in demented patients.
Insight was preserved in 2 of 7 patients and was partially intact in 2 others. Loss of insight was more likely in patients with dementia.
Patient 1 was a 75-year-old male with normal cognitive status. Within sleep-to-wake transitions, in the early morning or after a nap, he had the sensation that strips of paper or threads of wool were growing out of his palm and fingers. Sometimes this was only a sensation, but sometimes he saw them. He tried to remove them with the fingers of his other hand and roll them into a ball. While he was transitioning from sleep to wakefulness, his wife noticed he made strange hand movements. He explained these were in accord with his dreams. He also reported occasionally seeing fleeting images of shadows. Insight was intact. No treatment was instituted.
Patient 2 was a 92-year-old woman reported feeling “silk” threads coming out of her fingertips. She would remove them with the other hand and place them on her lap. Sometimes she also felt a cobweb round her fingers and occasionally had the sensation of someone familiar patting her on the shoulder. Passage, presence, and more structured visual hallucinations were also present. Treatment with quetiapine 25 mg at nighttime relieved the hallucinations.
Patient 3 was an 83-year-old man who felt yarn rolled around his index and middle finger while seated with hands on his lap. Using the other hand, he would unravel the yarn and wind it into a ball before leaving it on the table. He had passage hallucinations with preserved insight almost every day. No treatment was instituted.
Patient 4 was a 79-year-old man who felt threads in his hands. He played with them, changing them over from one hand to the other. These hallucinations occurred daily at any time during the day, but more frequently in the evening when he was sleepy. The phenomenon was recorded during an interview (see Video 1). He had also frequent visual hallucinations, present almost everyday, without insight. Hallucinations improved with rivastigmine 9.5 mg/day and quetiapine 25 mg/night.
Patient 5 was a 76-year-old man who felt “threads and hairs” around his fingers. He would play with them and make them into balls, then leave them on the table. He also had hallucinations of his deceased mother standing at his side. Insight was preserved. Hallucinations improved in both frequency and severity with donepezil 10 mg/day.
Patient 6 was an 85-year-old woman who felt and saw strings coming out of her hands. She made these into a ball that she left on the table or on her lap. She also saw children playing all around the house; they sometimes touched her and called her “grandma.” Insight was lost. The hallucinations did not disappear with aripiprazole 10 mg/day and rivastigmine 9.5 mg/day.
Shortly after initiating treatment with amantadine 200 mg/day, an 80-year-old woman (patient 7) complained of feeling and seeing threads on her fingers that she tried to unwind. She scratched her hands trying to remove the strands from her fingers, and caregivers consulted a dermatologist. She was considered to have an allergic reaction to amantadine and the drug was stopped. Although the hallucinations almost completely disappeared, they worsened again some months later, becoming threatening. Visions of unknown people in her house caused episodes of psychomotor agitation. All types of hallucinations improved with quetiapine 100 mg at night.
In striking coincidence with the first case, all patients shared a complex pattern of multimodal tactile and visual hallucinations. These hallucinations involved a thread-like condition that prompted interaction with the perceptions. Such interaction was noticed by family, caregivers, and external observers. Although multimodal hallucinations have been described in the literature,[2, 5] to our knowledge, this particular type of hallucination, involving the vision and tactile sensation of filaments emerging from fingers in association with a stereotyped behavior (fingering the threads), has not been previously reported in PD.
Several risk factors for the development of hallucinations have been identified in PD patients. These factors include cognitive impairment, stage of PD, antiparkinsonian treatments, and sleep alterations, especially rapid eye movement (REM) behavior disorder.[2, 3, 5, 8] In view of these risk factors, the development of hallucinations, including the string hallucinations in this report, was more likely in elderly patients, at advanced stages of PD (H&Y > 3), and with cognitive impairment. Interestingly, the only cognitively intact subject presented string hallucinations in the sleep-wake transition (hypnopompic hallucinations). This is probably related to a dissociated state of wakefulness and sleep, presenting intrusions of REM visual imagery into the wakefulness, as has been previously reported in the literature.[3, 8, 9] As we mentioned earlier, the role of antiparkinsonian drugs as a trigger for hallucinations in PD is well known. Along these lines, one of our patients (case 7) developed string hallucinations soon after initiating amantadine. In contrast, these string hallucinations, and also the other types of hallucinations in our patients, responded relatively well to low doses of antipsychotics. Moreover, hallucinations also responded to cholinesterase inhibitors, extending previous evidence on the cholinergic and dopaminergic bases of hallucinations in PD.[1, 2]
Finally, besides the string hallucinations, all our patients presented other types of hallucinations, mostly passage and presence, but some also had well-structured visual hallucinations. Only 1 patient had another type of multimodal hallucinations (tactile and auditory). Whereas minor hallucinations have been associated with decreased gray matter in the dorsal visual stream, indicating dysfunction of integrative perceptive areas, multisensory hallucinations in PD patients seem associated with a more widespread Lewy pathology extending to limbic and cortical areas.[10, 11]
Many types of hallucinations have been previously reported in PD. Our study identifies a previously undescribed type of hallucination in PD mostly present in demented patients. Extending routine screening for hallucinations may reveal a greater frequency of diverse psychotic phenomena in PD patients.