To the Editor:
I have read the interesting article by Karnath and Broetz on “pusher syndrome.”1 I think the article is very useful for physical therapist practice because it helps explain a little known problem that is frequently neglected by clinicians and researchers.
Other researchers,2–9 however, also have provided relevant and interesting information on this phenomenon, and I think it is useful to cite them. In particular, a number of findings have been reported on lesional sites and symptoms associated with the syndrome, and these findings are summarized in the Table. Reding et al,5 for example, performed a neuroimaging study that examined a number of lesional sites, and Premoselli et al6 and Perennou et al7 reported on large or multiple cortical-subcortical lesions related to the pusher behavior.
Some research6–8 revealed a strong association of pusher behavior with some aspects of neglect. According to Premoselli et al,6 personal neglect seems to be an important factor in the severity of the behavior. Perennou et al7 suggested that graviceptive neglect plays a role in the impairment of the processing of somesthetic inputs and could be the cause of pusher syndrome. La Fosse et al reported that there is a correlation of spatial neglect with ipsilateral pushing “resulting in a decreased sensitivity to the gravitational vertical with a directional bias in the perception of the origin of the spatial body axis.”8
Besides neglect, some authors2,8,9 also reported an association of pusher syndrome with sensory impairments. These impairments are probably not causally related to ipsilateral pushing, but they should be taken into account because they could be a key point for intervention.7,9
Based on their recent findings,10 Karnath and Broetz give a plausible and interesting explanation, which discusses neural and clinical correlates of pusher behavior. However, given the number of data on brain lesions and associated problems, we should be cautious in identifying specific correlates of this syndrome. I agree that further investigation is needed to clarify several aspects of this phenomenon and to be able to develop guidelines for physical therapy intervention.
- Physical Therapy
To the Editor:
Karnath and Broetz addressed a most vexing problem in their article Understanding and Treating “Pusher Syndrome.”1 They provide some intriguing information on the factors underlying the behavior. They suggest using visual aids to manage the problem. Although I do not contest the veracity of their reported experience, mine is different. Specifically, I have not found visual cues to be useful. Because “pushers” have a graviceptive perceptual impairment, I intervene on that impairment directly. I have described the motor relearning intervention in detail in a published case report.2 To briefly summarize here, the intervention involves allowing patients to realize their positional errors and their capacity to stand (or sit) independently when they act in accordance with facts that conflict with their misperception of body vertical.
To illustrate this intervention, I will use the example of a patient who, after a stroke, pushed strongly to his right. Intervention involved: (1) allowing the patient to repeatedly experience the consequence of his spontaneous self-determined position (ie, inevitable losses in balance toward his right), (2) having the patient recognize that what he perceived as safe and upright was not, and (3) using tactile and verbal feedback to orient the patient to true vertical. As I have often found for a subset of pushers, the patient could stand within 15 minutes following the intervention. I have not found the intervention efficacious for patients who have aphasia or are cognitively impaired, or who I believe are too anxious or reluctant to act in contradiction to their misguided sense of correct posture.
I do not know whether the approach I have described is superior to that advocated by Karnath and Broetz. Research is needed. It seems logical to me, however, that an intervention for patients with “a severe misperception of body orientation in relation to gravity”1(pp1122-1123) should involve the regaining of a sense of true body vertical and that such a sense does not have to be achieved via the visual system.
To the Editor:
I read with great interest and pleasure the article by Karnath and Broetz titled Understanding and Treating “Pusher Syndrome.”1 They discuss 2 graviceptive systems: the subjective visual vertical system (SVV) and the subjective postural vertical system (SPV). In the SVV, the receptors are the eyes and the vestibular system. The SPV (the damaged one in pusher syndrome) gives the body perception of its orientation in relation to gravity.
In my opinion, in order to determine a suitable intervention, we need to know what and where the receptors of the SPV are—knowledge that may offer us a different intervention approach. Mittelstaedt2 found a group of receptors situated in the abdominal cavity that are responsible for the SPV. Specifically, Mittelstaedt found: (1) pressure receptors situated in the kidneys, which according to Ammons3 are connected neurally to the cerebellum; (2) tension receptors situated in the ligaments connecting the big blood vessels to the spinal column; and (3) receptors in other internal organs. All these receptors constitute the SPV.
From this information, it may be possible to offer a different intervention approach than that suggested by Karnath and Broetz. Instead of using the uninvolved sensory system (SVV), physical therapists might attempt to facilitate the receptors of the involved receptors of the SPV. It is possible to do this by moving, passively or actively, the lower trunk on a stabilized upper trunk. I believe that this knowledge may help us to understand and manage other postural problems.
We thank Matteo, Bohannon, and Panturin for their interest and comments on our recent article on the “pusher syndrome.”1 As Matteo pointed out, it is also our experience that the pusher syndrome is highly associated with spatial neglect in patients after damage to the right hemisphere of the brain. Our investigation of this issue revealed that 80% of those patients with pusher syndrome due to right hemisphere damage exhibited additional spatial neglect.2 However, it is also known that pusher syndrome is a disorder that does not exclusively occur with right-side brain damage. It likewise is observed after left hemisphere lesions. Pedersen et al3 found left-sided damage in about 50% of a patient sample with pusher syndrome, while our own study2 revealed left-sided brain lesions in 35% of patients with pusher syndrome. All of these patients with left-sided lesions and pusher syndrome (including those described earlier by Davies4) did not show any signs of spatial neglect, either clinically or when formally tested. We thus agree with Pedersen et al3 that hemispatial neglect cannot be the cause of pusher syndrome.
We also agree with Bohannon that “allowing the patient to repeatedly experience the consequence of his spontaneous self-determined position” and “having the patient recognize that what he perceived as safe and upright was not” are powerful tools in physical therapy of pusher syndrome. Beyond the new feature we suggest, namely to use visual feedback to demonstrate actual body orientation, our intervention also includes these aspects mentioned by Bohannon. Unfortunately, the focus of our article and space limitations did not allow us to describe the new physical therapy procedure in detail. This is the topic of a recent article published elsewhere.5
Our physical therapy approach is based on the observation that visual-vestibular processing, and thus orientation perception of the visual surroundings, is not impaired in patients with pusher syndrome. Although these patients are no longer able to determine when their body is oriented in an erect position, they have no problems determining the orientation of the visual world around them correctly.6 This is the reason why we suggest including visual feedback of the patient's actual body orientation in physical therapy of pusher syndrome. Beyond our day-by-day observations in the clinical management of patients with pusher syndrome, there is now preliminary systematic evidence to suggest that this intervention approach can produce successful results. In 8 consecutively admitted patients with pusher syndrome, the time course of recovery was determined over a period of 3.5 weeks poststroke with daily physical therapy. Contraversive pushing improved significantly in this period. At day 24, 75% of the patients had recovered sufficiently to sit unsupported.7
We definitely agree with Panturin that a further approach to treat pusher syndrome would be to address directly the second graviceptive system in patients suffering from that disorder. She suggested to “do this by moving, passively and/or actively, the lower trunk on a stabilized upper trunk.” A general and important aim of future research in pusher syndrome thus will be to investigate and measure the effects of possible interventions on the patients' postural control and to find out which interventions, or combinations thereof, have the impact to shorten the time for inpatient care and to accelerate independence in daily living.