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=FINAL VERSION=

Stroke
Approximately 13% of all patients who develop aphasia following stroke have receptive aphasia. Stroke in the territory of the middle cerebral artery is the leading cause of receptive aphasia. The probability of middle cerebral artery strokes causing this disorder increases with age. Ischaemic strokes are the cause of 78% of receptive aphasia cases following stroke. In particular, ischaemic strokes due to cardiac emboli often affect the inferior division of the middle cerebral artery. This division irrigates the left brain hemisphere regions responsible for the functions impaired in receptive aphasia. Receptive aphasia following emboli occurs in 55% of cases due to ischaemic stroke, while 39% of these cases are due to cardiac emboli.

Haemorrhagic strokes may also lead to receptive aphasia. Haemorrhagic strokes may be due to hypertension, or due to the rupture of an aneurysm or arteriovenous malformation.

Trauma
Traumatic brain injuries in the form of focal contusions and closed head injuries also cause receptive aphasia. Contusions in the perisylvian region are a typical factor, since predominantly superficial lesions are sufficient for receptive aphasia to occur. Receptive aphasia is also present when focal contusions cause large lesions extending into the lateral temporal lobe or the white matter underneath it. Closed head injuries can consist of large subdural or epidural haematomas. In the presence of temporal contusion, such haematomas lead to a very severe receptive aphasia by causing occipito-temporal ischaemic strokes. Receptive aphasia is the second most frequent type of aphasia occurring after closed head injuries.

Tumours
Tumours are another cause of receptive aphasia, although a large tumour produces less impairment than an ischaemic stroke of the same size. This is due to the gradual disruption of function caused by tumours, which allows other parts of the brain to compensate for the loss of function. This usually leads to a slowly progressive receptive aphasia. However, the rate of growth and malignancy of the tumour also play a role in the speed of onset.

Other causes
Other causes of receptive aphasia include transient ischaemic attacks, migraine, and left temporal epileptic seizures. Such causes usually lead to transient aphasia, which may recur if the disease returns. Receptive aphasia may also appear as part of the migrainous aura, a phenomenon most likely due to the depression of neural activity induced by migraine. Language deterioration in Alzheimer's disease may also cause receptive aphasia before it progresses to global aphasia. Herpes simplex encephalitis is a rare condition which affects the medial temporal lobes and can thus cause receptive aphasia.

Causes of receptive aphasia in children
Traumatic brain injuries are the leading cause of receptive aphasia in children. Tumours are not likely to cause a specific type of aphasia such as receptive aphasia. In children, the lesions caused by herpes simplex encephalitis to the temporal lobe are much more severe compared to those caused by other damage, which may thus lead to receptive aphasia. The Landau–Kleffner syndrome, an age-related epileptic encephalopathy, may cause intermittent short episodes of receptive aphasia in children, with almost complete recovery between these episodes.

Assessment
The purpose of neurological and neuropsychological assessment of people with receptive aphasia is not only to diagnose the condition, but also to monitor change in symptoms over time and to devise a plan for therapy. As a consequence, examinations are not devised specifically for receptive aphasia. Rather, they are meant to assess a variety of language and other cognitive impairments present in aphasia and related disorders, in order to allow for differential diagnosis.

Clinical testing
In the acute phase of the disorder, the first assessment done is a bedside examination, usually part of a mental status examination administered by a neurologist. This examination includes tests of conversational speech, repetition, comprehension, naming or word finding, as well as, more briefly, reading and writing. The clinical test begins with an observation of the patient's conversational speech, which in receptive aphasia would be fluent and marked by paraphasias. Then, repetition is evaluated by asking the patient to repeat digits or single-syllable words, building up to complex sentences. A patient with receptive aphasia would have impaired repetition due to the inability to comprehend language. To test comprehension, the neurologist asks the patient to follow verbal commands increasing in complexity. Patients with receptive aphasia would have much difficulty comprehending these commands. A naming task consists of showing the patient various objects and actions and asking them to name them. Patients with receptive aphasia would be impaired on this task due to their anomia. While this clinical test is a very general overview of language functions, an experienced clinician would be able to draw preliminary inferences whether receptive aphasia is present.

Neuropsychological assessment
The neuropsychological assessment of aphasia is done in the non-acute phase of the disorder, and consists of psychometric tests administered by a neuropsychologist or a speech pathologist. There are two methods which can be used for the neuropsychological assessment of aphasia: aphasia screening tests and aphasia test batteries.

Aphasia screening tests
The aphasia screening tests are psychometric tests which may identify whether an aphasic disorder is present, but they are not generally used to diagnose receptive aphasia, as they are not as comprehensive as aphasia test batteries. A common screening test is the Token Test, which consists of twenty “tokens” in the shape of circles and squares, small and large, in five different colours. These tokens are laid out in front of the patient, who is asked to touch or manipulate a token of a specific shape, size, and colour, with instructions progressively increasing in complexity. The Token Test is useful for showing impaired comprehension in the case of receptive aphasia, and also tests for immediate memory span and syntax use.

Aphasia test batteries
In contrast to the screening tests, aphasia test batteries contain many different subtests which can generate a much more accurate description of the extent and quality of an aphasic impairment. These tests help distinguish between the different types of aphasic disorders, and can hence help a clinician diagnose receptive aphasia. Since they are much more comprehensive than screening tests, they usually require several hours to complete, and may be administered over the course of several days. Test batteries assess auditory and visual comprehension, word recognition, reading, writing, speaking and fluency, repetition, and naming. Some common test batteries in use include: the Boston Diagnostic Aphasia Examination and its abbreviated version, the Western Aphasia Battery; the Aphasia Diagnostic Profiles; and the Psycholinguistic Assessment of Language Processing in Aphasia.