TEMPORAL LOBE:

AUDITORY & VISUAL
EVOKED RESPONSE POTENTIALS (ERPs)

   The first component of the long latency auditory response (N1) had a significantly prolonged latency with lower amplitude in all patients with autistic behaviour (Seri et al, 1999)

   Autistic subjects demonstrated a lower amplitude of the P300 component (Niwa et al, 1983), as well diminished P300 are reported in ASD (Lotspeich, 1993).

   Recent investigations into hypothyrodism have also demonstrated prolonged P300 latency (Khedr et al, 2000).

   The acoustic evoked brain-stem response Jewett waves I-V were delayed in patients with hypothyroidism in comparison with an age-matched control  group (Hohmann et al, 1990).

   Nervous system dysfunction and hearing loss are part of the clinical picture of hypothyroidism. Several studies on visual evoked potential and two brainstem auditory evoked potential studies have shown abnormalities in this disease that are reversible with treatment(Vanasse et al, 1989).

   Data suggests that the period of greatest vulnerability to thyroid hormone depletion in the peripheral auditory system extends from at least 3 days before delivery through between 5 and 10 days of age (Hebert et al, 1985).

   A recent major study conducted in Spain on school-aged children showed clearly that  auditory threshold  is related to iodine intake and thyroid function (Soriguer et al, 2000).

   Visual evoked potential is reversibly altered in hypothyroidism (Ladenson et al, 1984).

    Influence of thyroid hormone supply on EEG frequency spectrum certainly has been established (Pohunkova et al, 1989;Khedr et al, 2000).

    It was found that visual evoked responses were abnormal in 12 of the 13 patients, the most common abnormality being an immature abnormal response pattern. Latency was increased significantly in 10 of the 11 patients who were diagnosed before the age of six months (Hrbek et al, 1982).

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Hebert R, Langlois JM, Dussault JH - "Permanent defects in rat peripheral auditory function following perinatal hypothyroidism: determination of a critical period" Brain Res 355(2):161-70 (1985) http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?uid=4084772&form=6&db=m&Dopt=r

Hohmann D, Kahaly G, Warzelhan J - "Effect of hyperlipidemia and hypothyroidism on auditory evoked brain stem responses" HNO 38(12):446-50 (1990) http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?uid=2086569&form=6&db=m&Dopt=r

Hrbek A, Fallstrom SP, Karlberg P, Olsson T - "Clinical application of evoked EEG responses in infants. III: congenital hypothyroidism" Dev Med Child Neurol 24(2):164-72 (1982) http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?uid=7095294&form=6&db=m&Dopt=r

Khedr EM, El Toony LF, Tarkhan MN, Abdella G - "Peripheral and central nervous system alterations in hypothyroidism: electrophysiological findings" Neuropsychobiology 41(2):88-94 (2000) http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?uid=10644929&form=6&db=m&Dopt=r

Ladenson PW, Stakes JW, Ridgway EC - "Reversible alteration of the visual evoked potential in hypothyroidism" Am J Med 77(6):1010-4 (1984) http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?uid=6507455&form=6&db=m&Dopt=r

Lotspeich LJ, Ciaranello RD -"The neurobiology and genetics of infantile autism (review)." Int Rev Neurobiol 35:87-129(1993) http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?db=m&form=6&uid=8463065&Dopt=r

Niwa S, Ohta M, Yamazaki K  - "P300 and stimulus evaluation process in autistic subjects" J Autism Dev Disord 13(1):33-42(1983) http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?uid=6222029&form=6&db=m&Dopt=r

Pohunkova D, Sulc J, Vana S - "Influence of thyroid hormone supply on EEG frequency spectrum" Endocrinol Exp 23(4):251-8 (1989) http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?uid=2620656&form=6&db=m&Dopt=r

Seri S, Cerquiglini A, Pisani F, Curatolo P - "Autism in tuberous sclerosis: evoked potential evidence for a deficit in auditory sensory processing" Clin Neurophysiol 110(10):1825-30 (1999) http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?uid=10574297&form=6&db=m&Dopt=r

Soriguer F, Millon MC, Munoz R, Mancha I, Lopez Siguero JP, Martinez Aedo MJ, Gomez-Huelga R, Garriga MJ, Rojo-Martinez G, Esteva I, Tinahones FJ - "The auditory threshold in a school-age population is related to iodine intake and thyroid function" Thyroid 10(11):991-9 (2000) http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?uid=11128728&form=6&db=m&Dopt=r

Vanasse M, Fischer C, Berthezene F, Roux Y, Volman G, Mornex R - "Normal brainstem auditory evoked potentials in adult  hypothyroidism" Laryngoscope 99(3):302-6  (1989) http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?uid=2918801&form=6&db=m&Dopt=r