Conduction aphasia
| Conduction aphasia | |
 | |
|---|---|
| Broca's area and Wernicke's area | |
| MeSH | D018886 |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ahmad Muneeb, MBBS[2] Synonyms and keywords: Dysphasia, Conduction; Associative Aphasia; Aphasia, Associative; Associative Aphasias; Dysphasias, Conduction; Aphasias, Associative; Conduction Aphasia; Conduction Dysphasias; Associative Dysphasias; Associative Dysphasia; Conduction Dysphasia; Dysphasias, Associative; Dysphasia, Associative; Aphasias, Conduction; Conduction Aphasias
Overview
Conduction aphasia, also called associative aphasia, is a relatively rare form of aphasia, thought to be caused by a disruption in the fiber pathways connecting Wernicke's and Broca's areas. The arcuate fasciculus has previously been implicated as this fiber bundle,[1] however more recent evidence suggests that the extreme capsule connects Wernicke's and Broca's areas[2].
Historical Perspective
- Conduction aphasia was first described by Carl Wernicke in the year 1874. At first, Wernicke hypothesized that conduction aphasia was caused by damage to a pathway running through the insula and connecting Broca's area and auditory association area but later the evidence proved that arcuate fasciculus was the main pathway involved in conduction aphasia. In 1885, Lichtheim described this disorder further.[3][4]
Classification
- [Disease name] may be classified according to [classification method] into [number] subtypes/groups:
- [group1]
- [group2]
- [group3]
- Other variants of [disease name] include [disease subtype 1], [disease subtype 2], and [disease subtype 3].
Pathophysiology
- The pathogenesis of conduction aphasia involves damage to arcuate fasciculus. Arcuate fasciculus is a white matter tract connecting Broca's and Wernicke's areas, the areas responsible for motor and sensory components of speech. Thus, when arcuate fasciculus is damaged the connection between Broca's and Wernicke's areas is lost. As a consequence, the transmission of information between the 2 speech centers is halted, leading to impairment of repetition.[5] Recent studies have indicated that conduction aphasia can result from brain damage to areas other than arcuate fasciculus, though the underlying mechanism involves disruption of connections between language centers. [6]
Causes
The most common cause of conduction aphasia is damage to arcuate fasciculus lying deep to left supra marginal gyrus. Other common causes of conduction aphasia include damage to other brain areas including leftsuperior temporal gyrus, left primary auditory cortices, insula and left inferior parietal lobe. Damage can be caused by multiple insults including stroke, tumors, infections. [7][8][5]
Differentiating conduction aphasia from other Diseases
- Conduction aphasia must be differentiated from other diseases that cause speech/language problems such as:[5]
Epidemiology and Demographics
- The prevalence of [disease name] is approximately [number or range] per 100,000 individuals worldwide.
- In [year], the incidence of [disease name] was estimated to be [number or range] cases per 100,000 individuals in [location].
Age
- Patients of all age groups may develop [disease name].
- [Disease name] is more commonly observed among patients aged [age range] years old.
- [Disease name] is more commonly observed among [elderly patients/young patients/children].
Gender
- [Disease name] affects men and women equally.
- [Gender 1] are more commonly affected with [disease name] than [gender 2].
- The [gender 1] to [Gender 2] ratio is approximately [number > 1] to 1.
Race
- There is no racial predilection for [disease name].
- [Disease name] usually affects individuals of the [race 1] race.
- [Race 2] individuals are less likely to develop [disease name].
Risk Factors
- Common risk factors in the development of [disease name] are [risk factor 1], [risk factor 2], [risk factor 3], and [risk factor 4].
Natural History, Complications and Prognosis
- The majority of patients with [disease name] remain asymptomatic for [duration/years].
- Early clinical features include [manifestation 1], [manifestation 2], and [manifestation 3].
- If left untreated, [#%] of patients with [disease name] may progress to develop [manifestation 1], [manifestation 2], and [manifestation 3].
- Common complications of [disease name] include [complication 1], [complication 2], and [complication 3].
- Prognosis depends upon the underlying etiology. If the conduction aphasia occurs as a result of stroke, then there is a probability of making a good recovery but persistent speech deficits may still remain. [5]
Diagnosis
Diagnostic Criteria
- The diagnosis of [disease name] is made when at least [number] of the following [number] diagnostic criteria are met:
- [criterion 1]
- [criterion 2]
- [criterion 3]
- [criterion 4]
History and Symptoms
- Symptoms of conduction aphasia may include the following:[5][9]
- impaired repitition
- paraphasic errors
- "conduit d’approache" (Often the responses are close to the target words, and the patient does repeated effort to correct the errors)
- abnormal confrontational naming
- Disturbed loud voice reading
- Speech fluency, reading, writing and comprehension may remain intact.
Physical Examination
- Physical examination is usually normal but may be remarkable for different findings depending upon the part of brain damaged. These may include:[9]
Laboratory Findings
- There are no specific laboratory findings associated with conduction aphasia.
Electrocardiogram
There are no ECG findings associated with conduction aphasia.
X-ray
There are no x-ray findings associated with conduction aphasia.
Echocardiography or Ultrasound
There are no echocardiography/ultrasound findings associated with conduction aphasia.
CT scan
Brain CT scan may be helpful in the diagnosis of underlying etiology of conduction aphasia. As conduction aphasia is caused by damage in dominant hemisphere so ct scan can show stroke, tumor, infection or other pathologies of dominant hemisphere. [5]
MRI
Brain MRI may also be helpful in the diagnosis of the underlying etiology of conduction aphasia, as it can identify the pathologies of dominant hemisphere including stroke, infection, tumor etc. [5]
Other Imaging Findings
There are no other imaging findings associated with conduction aphasia.
Other Diagnostic Studies
There are no other diagnostic studies associated with conduction aphasia.
Treatment
Medical Therapy
- There is no medical treatment for [conduction aphasia]; the mainstay of therapy is speech and language therapy. Most patients make a considerable recovery with speech and language therapy. [5]
Surgery
- There is no surgical treatment directed for improvement of aphasia. However, surgery can be performed to eradicate certain causes leading to aphasia like tumors or infections. [5]
Prevention
- There are no primary preventive measures available for conduction aphasia.
Presentation
Patients with conduction aphasia show the following characteristics:
- speech is fluent
- comprehension remains good
- oral reading is poor
- Major Impairment in repetition
- many phonemic paraphasias (phone substitution errors)
- transpositions of sounds within a word ("television" → "velitision") are common.
To understand the symptoms, recall that Broca's area is associated roughly with expression, Wernicke's area with comprehension.
With both areas intact but the neural connections between them broken, there is the curious condition where the patient can understand what is being said but cannot repeat it (or repeats it incorrectly). This patient will also end up saying something inappropriate or wrong, realize his/her mistake, but continue making further mistakes while trying to correct it.
References
- ↑ Essentials of Human Physiology by Thomas M. Nosek. Section 8/8ch15/s8c15_14.
- ↑ Schmahmann, J. and Pandya, D. "Fiber Pathways of the Brain". Oxford University Press 2006
- ↑ Hickok G (September 2009). "The functional neuroanatomy of language". Physics of Life Reviews. 6 (3): 121–43. doi:10.1016/j.plrev.2009.06.001. PMC 2747108. PMID 20161054.
- ↑ Benson, D. Frank (1973). "Conduction Aphasia". Archives of Neurology. 28 (5): 339. doi:10.1001/archneur.1973.00490230075011. ISSN 0003-9942.
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 Acharya AB, Maani CV. "Conduction Aphasia - StatPearls - NCBI Bookshelf". statpearls publishing.
- ↑ Benson DF, Sheremata WA, Bouchard R, Segarra JM, Price D, Geschwind N (May 1973). "Conduction aphasia. A clinicopathological study". Archives of Neurology. 28 (5): 339–46. doi:10.1001/archneur.1973.00490230075011. PMID 4696016.
- ↑ Jiménez de la Peña MM, Gómez Vicente L, García Cobos R, Martínez de Vega V (2018). "Neuroradiologic correlation with aphasias. Cortico-subcortical map of language". Radiologia. 60 (3): 250–261. doi:10.1016/j.rx.2017.12.008. PMID 29439808.
- ↑ Damasio H, Damasio AR (June 1980). "The anatomical basis of conduction aphasia". Brain : a Journal of Neurology. 103 (2): 337–50. doi:10.1093/brain/103.2.337. PMID 7397481.
- ↑ 9.0 9.1 Swanberg, Margaret M.; Nasreddine, Ziad S.; Mendez, Mario F.; Cummings, Jeffrey L. (2007). "Speech and Language": 79–98. doi:10.1016/B978-141603618-0.10006-2.