Acoustic-mnestic aphasia
Acoustic-mnestic aphasia is a speech disorder caused by an impairment of auditory-verbal memory. It is characterized by difficult repetition of the verbal chain, difficulties in choosing the necessary word in the course of a conversation. Diagnostics is made according to the results of speech therapy, assessment of neurological status, cerebral MRI, studies of cerebral hemodynamics, cerebrospinal fluid. Correction of aphasia is carried out against the background of treatment of the main causal pathology, includes speech therapy sessions, drug support, general rehabilitation (massage, exercise therapy).
General information
The term “acoustic-mnestic aphasia” was introduced and widely used by the founder of Russian neuropsychology, professor A.R. Luria. Some authors use the name “sensory-mnestic aphasia“. Pathology refers to the posterior forms of aphatic speech disorders. According to experts in the field of neurology and speech therapy, an isolated form of aphasia practically does not occur, usually, speech disorders are of a mixed nature with a simultaneous dysfunction of 2-3 mechanisms. Most often, acoustic-mnestic aphasia is observed in the acute period of stroke. The speech defect is not severely expressed, sometimes it remains unnoticed against the background of other neurological symptoms, in some cases it is mistaken for cognitive decline, a neurodynamic disorder.
The reasons
Pathology develops as a result of damage to the cortex of the mid-posterior parts of the middle temporal gyrus of the dominant hemisphere – 21 and 37 cytoarchitectonic fields of Brodmann. Changes in cerebral tissues can be ischemic, inflammatory, destructive, and compressive. Possible causes of damage are:
- Strokes. The most common cause of speech disorders. According to various sources, aphasia is observed in 30-60% of patients with stroke. In ischemic stroke, the mnestic form of aphasia occurs due to a lack of blood supply and hypoxia of the corresponding area of the cerebral cortex, in hemorrhagic stroke – as a result of compression of tissues by the poured blood.
- Traumatic brain injury. Contusion, crushing of cerebral tissues, the formation of an intracerebral hematoma leads to damage and death of neurons responsible for auditory-speech memory. The area of damage expands due to post-traumatic edema and inflammation.
- Intracerebral tumors. Primary and metastatic neoplasms in the temporal regions of the brain cause speech disorders in two ways. Invasively growing neoplasms cause destruction of the surrounding tissue. The delimited tumors, as they grow, begin to squeeze the cerebral structures and the vessels feeding them.
- Infectious and inflammatory diseases. Encephalitis, meningoencephalitis , cerebral abscesses with the location of foci of inflammation in the 21, 37 fields lead to dysfunction of the neurons responsible for speech. Inflammatory edema, compression, dysmetabolism in the affected area cause apoptosis of nerve cells, disruption of interneuronal connections.
- Progressive degenerative processes. The initial stages of Alzheimer’s disease, Pick’s disease, Schilder’s leukoencephalitis can occur with focal degeneration, demyelination of the region of the middle temporal gyrus. Progressive acoustical-mnestic dysfunction occurs, eventually turning into mixed sensorimotor aphasia.
Symptoms of acoustic-mnestic aphasia
A dissociation is typical between the impaired ability to repeat several words addressed to the patient and the normal reproduction of a single spoken word. Due to the limitation of auditory-speech memory, the patient is able to repeat the first and last, or only one word from the verbal chain. The patient explains this as a problem with memorization. The situation is repeated with repeated listening. Difficulty understanding long statements, simultaneous communication with several interlocutors. After listening to an instruction of 5-7 words, the patient grasps its essence but can perform with errors (for example, perform the specified action with another object).
Expressive speech is accompanied by difficulties in choosing the right word, which is associated with dysfunction of the optic-gnostic component. The resulting “blurring” of the meaning of words causes a large number of verbal paraphasias – not always suitable in terms of the meaning of verbal substitutions. Agrammatisms are represented mainly by the inconsistency of verbs, nouns, pronouns in number, and gender. The patient has difficulty expressing his own thoughts, describing pictures, composing a story in separate parts.
Dysgraphia is more pronounced when writing under dictation, it is characterized by a greater number of agrammatism than in oral speech. Patients do not remember well the dictated phrases, they are often asked to repeat their fragments, they are able to keep in memory no more than three words at a time. Dyslexia is observed when reading texts with sentences of considerable length. Auditory-verbal memory disorder causes the inability to keep the readable text in the head, which leads to misunderstanding of the read. Akalculia is expressed in the difficulty of arithmetic operations with multidigit numbers since the patient cannot remember the numbers transferred from one category to another.
Diagnostics
The acoustical-mnestic form is not obvious; for its identification during the initial consultation of the patient, a comprehensive study of the speech function is necessary. Diagnostics is carried out by the joint efforts of a number of specialists: a neurologist, aphasiologist, neuropsychologist, psychiatrist. Since the diagnosis of “aphasia” is syndromological, clarification of the etiology of the process is required. A comprehensive examination of the patient includes:
- Neurological examination. In the neurological status, a concomitant focal neurological deficit is found: spastic hemiparesis, cranial nerve pathology. Assessment of cognitive abilities is of great importance. In case of deviations in mental status, consultation with a psychiatrist is required.
- Diagnostic examination of speech. It is carried out by a speech therapist-aphasiologist in a complex manner. Revealed verbal paraphasia, agrammatism, decreased auditory-speech memory, dyslexia, dysgraphia. Optical-gnostic dysfunction is diagnosed by the absence of distinctive details of the object in the patient’s drawings: the handle at the cup, the spout at the teapot.
- MRI of the brain. Allows you to determine the morphological substrate of the disease. Visualizes tumor processes, inflammatory foci, degenerative changes, ischemic zones, intracranial hematomas, traumatic injuries.
- Vascular research. Doppler ultrasound, duplex scanning, and MR angiography are prescribed for suspected cerebrovascular pathology. They help to confirm changes in cerebral blood flow, vessel occlusion, to assess the state of collateral circulation.
- Lumbar puncture. Produced in the presence of clinical data for neuro infection in order to obtain and study cerebrospinal fluid. When conducting laboratory tests, inflammatory changes, a specific pathogen, tumor cells, signs of hemorrhage are determined.
Acoustic-mnestic aphasia is differentiated from other speech disorders. Active expressive speech makes it possible to exclude motor aphasia, in which speech production is sharply limited. Unlike acoustic-gnostic aphasia, the mnestic form is characterized by more complete utterances, the absence of literal paraphasia, “speech salad”. A thorough examination of speech makes it possible to distinguish aphasia from cognitive impairment.
Pathogenesis
Articulation of speech, phonemic hearing is normal. The pathogenetic basis of this speech disorder is a violation of auditory-speech memory. According to the assumptions, patients have increased inhibition of auditory-speech traces. Clinically, this is expressed by forgetting the previously heard words when perceiving new ones. Another pathogenetic aspect of this pathology is the limited volume of auditory-speech memory. The defect negatively affects the ability to write, count, and read.
In most cases, the defeat of the posterior temporal areas (field 37) is accompanied by a violation of their connection with the nearby optic-gnostic structures of the occipital lobe. As a result, difficulties arise in the relationship between the verbal designation of an object and its visual image, the semantic side of speech suffers. The consequence is the clinically observable difficulty of perceiving what was said and the difficulty of choosing the necessary words in expressive speech.
Treatment of acoustic-mnestic aphasia
Correction of a speech defect is carried out against the background of compulsory therapy of the underlying pathology. Depending on the type of stroke, thrombolytic or hemostatic therapy is performed. In the case of a tumor, hematoma, together with neurosurgeons, the possibility of radical removal, radiotherapy is considered. Patients with neuroinfection are prescribed etiotropic antibacterial or antiviral treatment. Therapy of actual speech disorders includes two components:
- Speech therapy classes. The task of speech therapy correction is to expand the volume of the operative auditory-speech memory. If possible, classes begin from the first days of the disease and are carried out in stages with a gradual build-up and complication. Initially, tasks are performed based on visual perception, then short auditory dictations are given. It is recommended to memorize and recall speech lines, poems, songs. Difficulties in choosing words in speech are overcome by clarifying their meaning, systematizing, comparing synonyms and antonyms.
- Pharmacotherapy. It is necessary to stimulate metabolic processes in the brain, restore lost neural connections and functions. It is produced by vascular (vinpocetine), nootropic (piracetam), neurometabolic (gamma-aminobutyric acid) drugs. In the treatment of aphasia, the drug memantine has proven itself well.
During the rehabilitation period, the patient needs the help of loved ones. Productive communication is possible subject to a decrease in the rate of speech, the exclusion of long complex statements. Maintaining verbal contact on the part of relatives, assistance in performing speech therapy exercises at home contribute to the early restoration of speech function. Speech therapy rehabilitation is effective against the background of restorative exercise therapy, massage, psychotherapy.
