Evidence-based Compensatory and Restorative Treatments
Studies investigating the value of SLT for aphasia have been undertaken for decades; however, converging evidence in favor of SLT has only recently emerged. One reason for the delay may be that randomized, double-blind, controlled trials, a gold standard for evidence-based practice, are especially difficult to conduct for SLT. One major limitation is that access to SLT has been the established standard of care for aphasia for quite some time in many parts of the world; it can be difficult to randomly assign patients suffering from the disorder to a no-treatment group during a potentially crucial phase of their recovery. Another limitation comes from the potential for bias in empirical research; blinding the researcher to treatment arms is difficult and blinding the patient is nearly impossible. A third major limitation arises from the heterogeneity in the disorder as well as in the treatment approaches used. For example, significant positive effects for individuals or for specific subpopulations of persons with aphasia may be overshadowed by attempts to generalize across entire groups of participants with various types of aphasia.
Despite these limitations, evidence is emerging that establishes SLT as an effective method for enhancing language recovery after stroke. The American Speech–Language Hearing Association, the professional association for SLPs, defines the three components of evidence-based practice (EBP) for aphasia therapy as external scientific evidence, clinician expertise, and patient perspectives. Because of the aforementioned barriers to obtaining gold-standard scientific evidence in the field of aphasia, all three components of EBP are especially important in evaluating aphasia treatment approaches.
Acute Recovery (Up to 3 Weeks)
The acute recovery phase is characterized by spontaneous recovery of function, as there is physiological restitution of the damaged brain. There is no strong evidence that SLT can boost the effects of spontaneous recovery in the first 3 weeks after stroke; in contrast, there is some evidence in the motor literature, based largely on animal research, that intensive intervention in the very early stages may adversely affect recovery. Although there is debate about what constitutes the acute phase (estimates range from ~1 week–1 month), it has been demonstrated that intensive intervention in this initial acute phase can be counterproductive to ultimate motor recovery in humans as well. On the other hand, there is also evidence that complete disuse of impaired functions after stroke can be detrimental to later recovery of function. In the absence of specific evidence, however, a balanced approach to early intervention may be warranted. There is currently a push toward an increased focus on counseling and support in the highly acute phase of SLT, as opposed to immediate attempts at impairment-based intervention. Such an approach is based on reports from patients and families about the types of support they would have wanted in the early stages, although there is not yet prospective evidence regarding how this approach impacts outcomes or patient satisfaction.
Subacute Recovery (3 Weeks–12 Months)
Spontaneous recovery often continues during the subacute phase, but this is more likely due to functional reorganization of the brain as opposed to the physiological restitution seen in the acute phase. Two recent Cochrane reviews have made significant strides toward establishing SLT as an effective treatment for aphasia, beginning in the subacute phase. The authors of the 2012 review note that the primary purpose of language is to convey meaning, so the primary outcome measure taken from the 39 studies included was functional communication, defined as "the ability to successfully communicate a message via spoken, written, or nonverbal modalities (or a combination of these) within day-to-day interactions." The general conclusions of these meta-analyses are that SLT facilitates improvement in functional communication, expressive language, and receptive language when compared with no SLT and that social stimulation alone is not as effective as participation in formal SLT. However, these effects are both modest in size. An earlier meta-analysis and multiple smaller studies have made strides to establish the efficacy of SLT on a smaller scale.
One limitation of the meta-analyses is that they necessarily combine data across studies using considerably different types of SLT for aphasia. There are a variety of specific approaches to SLT for aphasia, but a major distinction can be drawn between methodologies that apply therapeutic restriction to the verbal modality, such as constraint-induced language therapy, constraint-induced aphasia therapy, and intensive language action therapy, and those that encourage use of nonverbal modalities. This latter group originally focused on the use of other communicative modalities (e.g., gestures) to compensate for verbal deficits, such as promoting aphasics' communicative effectiveness (PACE) or drawing therapy. Evidence for each of these therapies indicates that at an appropriate intensity, they can be effective in improving communication skills in both subacute and chronic patients. Newer versions of nonverbal therapies use other communicative modalities not to compensate for deficits in verbal output, thereby replacing speech, but rather as a supportive cue for improving verbal ability; emerging evidence supports their effectiveness. There are relatively few studies directly comparing these different types of SLT; the 2012 Cochrane review found that very few generalizable conclusions could be drawn from such studies.
Chronic Recovery (>12 Months)
Traditional approaches to aphasia treatment suggested that the opportunity for recovery had largely ended by the time patients entered the chronic phase. Newer research, including the systematic reviews described above as well as case studies, indicates that this is not the case and that there is an opportunity for improvement of language function throughout the lifetime of an individual with aphasia. In contrast to research suggesting potentially negative impacts of early intensive treatment, evidence supports the benefits of high-intensity SLT in the chronic phase. A systematic review of previous studies by Bhogal et al in 2003 showed that positive evidence for the efficacy of SLT comes from studies with higher intensity of treatment (mean of 8.8 hours a week), whereas negative evidence comes from studies using SLT at lower intensities (mean of 2.0 hours a week). A systematic review by Allen et al in 2012 supported the importance of intensity in treatment for chronic aphasia; it also reviewed evidence that computer-based therapies, group language therapies, communication partner training, and constraint-induced therapy are effective approaches when initiated in the chronic phase (i.e., > 6 months after stroke).
In addition to these more traditional approaches to SLT, the chronic phase of recovery is a time when patients may appreciate referrals to other resources, such as aphasia centers, mentorship programs, and stroke support groups. Although there are no randomized controlled trials to provide evidence for this type of treatment for chronic aphasia, some evidence for their benefit exists on a smaller scale (for a list of such resources, please see the website of the National Aphasia Association at http://www.aphasia.org).
Overall, it has been established that speech–language therapy generally improves outcomes in patients with aphasia, but additional research is needed regarding specific approaches. Generally, there has been an expansion from the use of a strictly impairment-based treatment to the inclusion of treatments that incorporate aspects of the individual's functional communication, such as multimodality approaches to treatment, and the Life Participation Approach to Aphasia, but more evidence is needed to support the efficacy of these approaches. Additionally, there has been much recent research on brain plasticity; this research has identified many principles of neuroplasticity that can be applied to stroke rehabilitation in general and aphasia in particular. These principles include timing, intensity, salience, "use it or lose it," and generalization. The optimal parameters for these principles with respect to aphasia, including the most effective method for treating specific patterns of deficits in aphasia, have yet to be determined. Additional research is needed to investigate the relative efficacy of SLT for aphasia at different time points in recovery, and whether particular approaches to treatment may be most beneficial at specific times after the injury.