Since<unk>  and auditory agnosia have many similarities, diagnosing the disorder proves to be difficult. Bilateral lesions near the primary auditory cortex in the temporal lobe are important criteria.<unk>  requires demonstration that brainstem auditory responses are normal, but<unk>  evoked potentials are impaired. Brainstem auditory evoked potentials (BAEP), also referred to as brainstem auditory evoked responses (BAER) show the neuronal activity in the auditory nerve, cochlear nucleus, superior olive, and inferior colliculus of the brainstem. They typically have a response latency of no more than six milliseconds with an amplitude of approximately one microvolt. The latency of the responses gives critical information: if<unk>  is applicable, LLR (long-latency responses) are completely abolished and MLR (middle latency responses) are either abolished or significantly impaired. In auditory agnosia, LLRs and MLRs are preserved. Another important aspect of<unk>  that is often overlooked is that patients feel deaf. They are aware of their inability to hear environmental sounds, non-speech and speech sounds. Patients with auditory agnosia can be unaware of their deficit, and insist that they are not deaf. Verbal deafness and auditory agnosia are disorders of a selective, perceptive and associative nature whereas<unk>  relies on the anatomic and functional disconnection of the auditory cortex from acoustic impulses. Case examples Although<unk>  has very specific parameters of diagnosis, its causes on the other hand can vary tremendously. The following are three case studies with different reasons for<unk> . # A case published in 2001 describes the patient as 20-year-old man referred for cochlear implants because of bilateral deafness following a motorcycle accident two years earlier. His CT shows hemorrhagic lesions involving both internal capsules. He was comatose for several weeks and awoke quadriparetic, cognitively impaired and completely deaf. He exhibited a response towards the occasional sudden, loud sound, however, by turning his head. Reading and writing capabilities were maintained, and he was able to communicate by lip-reading. His own speech was dysarthric, but comprehensible. Normal tympanograms and stapedial reflexes imply that the middle and inner ear remained functioning and the auditory nerve was intact. His auditory nerve was tested by evoking responses with normal auditory nerve potentials at 10 dB bilaterally. The results of the BAER waves were normal, but an abnormal complex IV-V suggested that the pathways were functioning through the brainstem, but there was a lesion present in the mid-brain. With these findings, it was determined the patient had<unk>  due to bilateral interruption of the ascending auditory pathway associated with hemorrhagic lesions of both internal capsules. Therefore, cochlear implantation was not performed. # Published in 1994, this patient was monitored over the course of almost 20 years after exhibiting signs of hearing impairment as an infant. Audiologic and related test results in concurrence with MRI confirmed bilateral absence of considerable portions of her temporal lobes resulting in<unk> . Although physiologic measures demonstrate normal peripheral hearing sensitivity, this patient's speech has the inflection and prosodic characteristics associated with profound peripheral hearing loss, and she is unable to understand spoken communication. Behaviorally obtained pure-tone thresholds were variable, ranging from normal to moderate hearing loss with normal middle ear muscle reflexes and normal ABRs to high- and low-intensity stimuli. Auditory middle latency and<unk>  evoked potentials were grossly abnormal, consistent with the central nature of<unk> . Because of her inability to communicate auditorily, this patient was ultimately taught American Sign Language and educated at the Louisiana School for the Deaf. At the completion of the case study, the patient was married and expecting a child. # A more recent study, published in 2013 the patient described is a 56-year-old woman a history of hypertension, hypercholesterolemia, and multiple cerebrovascular accident (CVA) who presented in March 2009 with a complaint of complete bilateral hearing loss. In March 2009, she experienced an acute right-sided insulotemporal intracerebral hemorrhage. Immediately after this event, the patient complained of hearing loss with the inability to hear all sounds except for severe bilateral tinnitus. Imaging revealed sequelae in the left cerebral cortex from her previous CVA. The new right-sided hemorrhage was centered on the posterior putamen with surrounding edema involving the posterior portion of the posterior limbs of the internal, external, and extreme capsules. Signal abnormalities extended into the right temporal lobe. The patient had no other neurologic deficits and spoke fluently, although with poor internal volume control of her voice. Otoscopic examination revealed normal-appearing external auditory canals, intact tympanic membranes bilaterally, and normal middle ear anatomy. Audiogram at that time showed bilateral profound hearing loss with no responses to pure-tone or speech testing.
Cortical deafness
Post-lingual deafness
Nonsyndromic deafness
Prelingual deafness
Childhood blindness
Optic nerve hypoplasia
Surface dyslexia
Phonological dyslexia