Semantic aphasia symptoms classification diagnostic correction
Semantic aphasia is a systemic speech disorder that occurs when the temporo-parietal-occipital junction of the left hemisphere is affected. It is characterized by a violation of the understanding of semantics, complex grammatical structures, a disorder of visual-spatial gnosis, acalculia, and elements of apraxia. Diagnostics includes speech therapy and neurological examination, cerebral neuroimaging, study of cerebral hemodynamics, analysis of cerebrospinal fluid. Speech therapy correction is carried out in stages against the background of etiopathogenetic therapy and rehabilitation treatment.
Semantic aphasia was first described by the English neurologist Henry Head, then studied in detail by the Russian scientist A.R. Luria. Pathology is a disorder of a deep understanding of the meaning of a word in the context of subtle logical-grammatical speech structures. Since aphasia is based on a violation of the perception of the semantics of a word, in speech therapy it is called “semantic”. This type of speech impairment is considered as an integral part of TPO syndrome, which occurs in the pathology of the cerebral cortex at the junction of the temporal (temporal), parietal (parietal) and occipital (occipital) lobes. Most often, semantic aphasia occurs as a result of a stroke in middle-aged and elderly patients.
TPO syndrome develops as a result of damage to the cortex of the tempo-parieto-occipital junction. Among the direct causes of pathology, the main share belongs to acute cerebrovascular disorders (strokes), the risk factors of which are atherosclerosis , arterial hypertension , atrial fibrillation, valvular defects, diabetes mellitus , cerebrovascular vasculitis . Other possible etiological factors are:
- Brain tumors . Invasive intracerebral tumors (glioblastomas, medulloblastomas ) TPO localization invade the surrounding tissues, destroying the cortex and its connections with underlying structures. Non-invasive neoplasias compress the cortex as they grow, resulting in dysfunction and neuronal death.
- Traumatic brain injury . There is a direct damage to the neurons of the TPO zone at the time of injury or their subsequent compression by an increasing post-traumatic hematoma. Possible iatrogenic injury to the cortex during neurosurgical interventions.
- Inflammatory processes . Encephalitis , meningoencephalitis, brain abscesses of specific ( tuberculosis , syphilis ) and nonspecific (bacterial, viral, fungal) etiology cause the development of inflammatory changes. Under conditions of inflammation, dysfunction of the neurons of the cortex occurs, and semantic aphasia appears.
- Neurodegenerative diseases . In the initial period, progressive cerebral neurodegeneration (for example, Alzheimer’s disease) causes moderate dysfunction of TPO junction neurons. Then, progressive atrophy of the cortex leads to more severe mixed speech disorders.
Etiofactors cause damage to the temporal-parieto-occipital region of the cerebral cortex (fields 21, 37, 39, 40 according to Brodman), which are tertiary fields of the block for receiving, processing and storing exteroceptive information. The task of these fields is to combine polymodal information (simultaneous synthesis). Semantic aphasia occurs due to disorders of these functions, which are necessary to combine the details into a single whole. The primary understanding of the word associated with its sound has been preserved. Violations relate to the process of further clarifying the meaning of the word in the context of the sentence, which leads to defects in understanding the addressed speech . In parallel, there are disorders of spatial perception, constructive apraxia , elements of specific amnesia with the difficulty of finding the individual necessary to form the utterance of words.
In the literature, the concept of the severity of this pathology is blurred. Most authors believe that there are predominantly mild and moderate degrees of impairment. However, the instructions of individual specialists on the cases of grossly expressed symptoms observed by them made it possible to distinguish also a severe degree. Thus, semantic aphasia is classified into 3 degrees of severity:
- Easy. The establishment of cause-and-effect relationships has been violated. Difficulties arise in the selection of synonyms and antonyms, the interpretation of complex speech turns. Difficulties in solving logical problems are observed.
- Moderately heavy . Comprehension of logical-grammatical constructions and figurative meaning of words is difficult. Significant difficulties in solving mathematical problems, performing counting operations are noted.
- Heavy . Severe visual-spatial perception disorders: apractoagnosia, acalculia , violation of the body scheme . Understanding of grammatical turns and prepositional-case constructions is not available.
Symptoms of semantic aphasia
In the clinical picture, gross speech disorders are absent. Phrasal expressive speech is usual in volume and tempo, but it is built with simple sentences without the use of complex syntactic constructions. Agrammatisms are possible. The patient perfectly understands individual words and simply constructed speech. The complication of the speech structures used by the interlocutor causes misunderstanding and confusion. The perception of participial and adverbial phrases, syntactic constructions reflecting a causal relationship, spatial arrangement is difficult. The meaning of sayings, proverbs, metaphors, common expressions is lost – they are taken literally, interpreted in the direct meaning of words.
The patient’s understanding of the semantics of a word is impaired: words are perceived in detail without taking into account their grammatical form. For example, the nouns “run”, “jump” are referred to by patients as verbs, and the verbs “to turn green”, “to be prettier” – to adjectives. Violation of understanding the grammatical category of a word (parts of speech, gender, case, number) makes it impossible to follow instructions such as “Show the glass with a pencil”, “Show the mirror with a pointer.”
Semantic aphasia is combined with visual-spatial agnosia – a distorted perception of the spatial relationship of objects. As a result, the understanding of speech structures with prepositions (under, over, on, in), comparative forms (less, more), attributive genitive (father’s coat, driver’s car), temporal turns (before the weekend, after winter) is impaired. The perception of geographical maps, orientation by the clock is impaired. There is a spatially constructive apraxia – the patient is not able to position objects according to the task “a pen to the left of the ruler and to the right of the eraser”. Loss of orientation in numerical digits and constructive apraxia make it difficult to consistently perform a number of counting operations, and acalculia develops.
In some cases, semantic aphasia is accompanied by amnestic difficulties, expressed in the difficulty of finding the name of an object or concept when constructing statements. In such situations, patients use the syntagmatic method of describing a function (“what they draw with”) or call the categorical affiliation of an object (“such furniture”). Written speech is simplified, does not contain complex grammatical turns. Reading is safe, but difficulties arise in understanding long sentences with a complex structure.
Because semantic aphasia is rarely gross, it is often overlooked by neurologists. Identification of speech disorders is possible only when performing special tasks. Verification of the type of cerebral lesion requires instrumental studies. The following examinations are of the greatest diagnostic value:
- Neurologist’s consultation. Includes the collection of anamnesis: the presence of TBI, contact with an infectious patient, the first signs of the disease, the nature and pace of their development. In the neurological status, asymmetry of reflexes, moderate right-sided hemiparesis, and hemihypesthesia are possible. With the help of special testing, a disorder of spatial gnosis and praxis, acalculia, is revealed.
- Speech therapist consultation . Diagnoses difficult perception of complex utterances, violations of word semantics, spatial-constructive relationships, elements of amnesia when searching for the required word. The study of auditory-speech memory does not determine pathology. Articulation is completely preserved. Writing and reading is difficult when dealing with grammatically complex sentences.
- MRI of the brain . Neuroimaging of the TPO zone makes it possible to determine the size and nature of its lesion. Most often, post-stroke foci are observed. It is possible to identify inflammatory foci, atrophic foci, abscess, tumors, brain cysts. In case of contraindications to MRI, the presence of a hematoma, a cerebral CT scan may be required.
- Cerebrovascular studies. Assessment of hemodynamics is carried out using transcranial ultrasound , duplex scanning, MRI of cerebral vessels . The examination makes it possible to diagnose hemodynamic disorders in the basin of the left middle cerebral artery.
- Lumbar puncture . It is performed under the assumption of the presence of neuroinfection. It makes it possible to assess the cerebrospinal fluid pressure and obtain cerebrospinal fluid. In the case of an inflammatory nature of the disease, analysis of the cerebrospinal fluid reveals cytosis with a predominance of leuko- or lymphocytes, a moderate increase in protein.
Differential diagnosis is carried out with other speech disorders. Aphasia differs from dysarthria in the complete preservation of the functioning of the articulatory organs. In contrast to the acoustic-gnostic, acoustic-mnestic aphasia , the semantic aphasia proceeds with the preservation of phonemic perception, auditory-speech memory. Dynamic aphasia is characterized by the limitation of expressive speech, stereotyped utterances, semantic aphasia – by the normal volume of speech production.
Semantic aphasia treatment
Speech rehabilitation begins against the background of etiotropic therapy aimed at eliminating the causative pathology, and continues in parallel with other methods of restorative treatment. Since a mild speech defect does not significantly limit the patient’s communicative abilities, its correction is carried out if the patient is aware and wants to correct the existing dysfunction. Rehabilitation work is carried out by a neurologist, speech therapist, neuropsychologist, rehabilitologist against the background of medication neuroprotective therapy with nootropics, neurometabolites, vasoactive pharmaceuticals. The main stages of speech therapy correction are:
- Restoration of visual-spatial perception . Achieved by exercises with drawing up pictures, arranging objects according to the task, indicating cause-and-effect relationships. In case of gross manifestations, an analysis of the body scheme is carried out.
- Restoration of semantics . The analysis of various grammatical forms of the word, the differentiation of logical and grammatical turns, the selection of synonyms / antonyms, the interpretation of persistent speech utterances is carried out. The use of words in various grammatical constructions is being developed.
- Recovery of counting operations. Severe semantic aphasia requires the restoration of the perception of mathematical signs, the ability to solve the simplest examples. With an average severity of violations, the stages of solving complex mathematical expressions are analyzed, with an easy one – logical problems.