There are several forms of aphasia, or a disorder of language, that can gradually worsen over time. These are not due to head trauma, stroke, cancer or other observable secondary changes in the brain, and hence appear to be intrinsic disorders of brain functioning – as such, we refer to this class of conditions as “primary.”
Several primary features characterize the logopenic variant of Primary Progressive Aphasia (PPA). One characteristic feature is profound difficulty with repetition and very short-term memory. Thus, these individuals have difficulty repeating brief phrases, and have difficulty repeating a short sequence of numbers. Individuals with the logopenic variant of PPA also have difficulty with naming objects. Word comprehension tends to be relatively preserved, and the naming deficit in logopenic variant PPA appears to be due instead to difficulty retrieving the lexical form of the word.
In addition to difficulty with repetition and naming, individuals with the logopenic variant of PPA can have other deficits. Among these may be difficulty with fluent speech, or impaired comprehension of single words (although comprehension of objects is well preserved). Because of this variability, this among the most difficulty of PPA conditions to diagnose.
Over time, many individuals with the logopenic variant of PPA can develop a disorder of episodic memory. Due to difficulty with learning and remembering, individuals can repeat themselves in the course of a conversation, ask the same question repeatedly during the course of a day, and forget events and conversation that recently occurred. Disorientation in place and time can emerge.
Detailed MRI studies of the logopenic variant of PPA show subtle atrophy in the core language regions of the left hemisphere. This includes the frontal lobe, parietal lobe, and temporal lobe. Over time, the atrophy can involve the hippocampus, an area deep in the temporal lobe that is important for memory.
In about 70% of individuals with the logopenic variant of PPA, inspection of the brain at autopsy reveals the accumulation of amyloid plaques and tau neurofibrillary tangles. These are the microscopic characteristics of Alzheimer’s disease. These individuals with the logopenic variant of PPA thus can be thought to have an unusual variant of Alzheimer’s disease that begins by affecting the language regions of the brain. Eventually, as the condition progresses, it may begin to affect the memory regions that are typically involved in most cases of Alzheimer’s disease. In the remaining 30% of cases, microscopic inspection of the brain reveals an accumulation of tau inclusions in the brain cells that are often seen in the non-fluent/agrammatic variant of PPA.
It is possible to identify the cause of the logopenic variant of PPA by inspection of the cerebrospinal fluid (CSF). This is the fluid that bathes the brain and spinal cord, and thus contains some of the proteins that are found in the brain. Rather than performing a brain biopsy to study the brain during life, a lumbar puncture (also known as a spinal tap) can be performed.
There are two kinds of treatments available for individuals with the logopenic variant of PPA. First, medication treatments can be borrowed from among those available for Alzheimer’s disease. These may help slow down the decline in memory and language. Second, individuals with the logopenic variant of PPA can take advantage of behavioral and speech therapies and improve their own naming and comprehension skills through practice in normal conversations. Some individuals benefit from a picture dictionary. Communication efficacy is enhanced when conversing in a familiar environment at a slow speech rate, supplemented by gestures. Computer devices can hold prerecorded phrases and sentences that the patient can use to assist communication. Memory can be supplemented by developing the habit of writing down key appointments in a calendar book.
In addition to performing more detailed studies to characterize patients with the logopenic variant of PPA, scientists at the Penn FTD Center have developed techniques to study the CSF, perform detailed analyses of MRI scans, and to relate language, MRI and CSF characteristics together to provide an accurate diagnosis of patients with PPA so that the most effective treatments can be applied.