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Auditory Neuropathy Spectrum Disorder: Issues in Diagnosis and Management Thierry Morlet, PhD [email protected] Overview of Auditory Neuropathy Definition Auditory neuropathy is a relatively recent clinical diagnosis. Describe individuals with auditory disorders due to dysfunction of the inner hair cells, of the synapses between the inner hair cells and the auditory nerve, and/or the auditory nerve. Unlike patients with sensory hearing loss who show clinical evidence of impaired outer hair cell function, patients with auditory neuropathy show clinical evidence of normally functioning outer hair cells. Individuals with auditory neuropathy typically demonstrate impaired speech understanding, and show normal to severely impaired speech detection and pure tone thresholds. Auditory neuropathy affects an individual’s ability to process rapidly changing acoustic signals, known as auditory temporal processing. Auditory Neuropathy Spectrum Disorder Patients with outer hair cell responses and absent/abnormal auditory brainstem responses, are classified as having: - AN: auditory neuropathy* - AN/AD: auditory neuropathy/dys-synchrony** - ANSD: auditory neuropathy spectrum disorder*** * Starr A, Picton TW, Sininger Y, Hood LJ, Berlin CI. 1996. Auditory neuropathy. Brain, 119:741-753. ** Berlin C, Hood L, Rose K. 2001. On renaming auditory neuropathy as auditory dys-synchrony: Implications for a clearer understanding of the underlying mechanisms and management options. Audiology Today 13:15-17. *** Auditory neuropathy consensus conference. J Gravel, 2008, Como, Italy Auditory Neuropathy Auditory Neuropathy/Dys-synchrony Auditory Neuropathy Spectrum Disorder Clinical Presentation Problems listening in noise, fluctuation, delayed speech/ language development Physiologic Responses Hair Cell Responses Present otoacoustic emissions Present cochlear microphonics Neural Responses Absent auditory brainstem responses Absent middle ear muscle reflexes No suppression of otoacoustic emissions Behavioral Responses Variable audiometric configurations Variable but generally poor speech recognition What is the occurrence of ANSD? • About 1 in 10 patients with desynchronized ABRs will have OAEs and/or cochlear microphonics. • This prediction is based on research from: • Berlin, Hood, Morlet, Keats et al., 2000 – Of 1000+ children screened in schools for the Deaf, 10-12% had either robust OAEs or evidence of residual OHC function. • Lee et al., 2001 - Of 72 students at schools for hearing-impaired, approximately 10% had either robust OAEs or evidence of OHC responses. • Rance et al., 1999 – 1 in 9 infants with permanent hearing loss had cochlear microphonics but no ABR. • Sininger, 2002 – Approximately 10% of infants had OAEs and no ABR in the NIDCD Newborn Screening Study. Outer Hair Cells MOTION AMPLIFIERS OUTER HAIR CELLS MISSING IHCs OK Inner Hair Cells (IHC) SEND NEURAL PULSES TO THE BRAIN (a) NORMAL HEARING (b) SENSITIVITY LOSS Harrison RV. An animal model of auditory neuropathy. Ear & Hearing. 19(5):355-61, 1998 Oct Special thanks to Mead Killion,Ph.D. OHCs OK INNER HAIR CELLS MISSING (c) CLARITY LOSS Auditory Neuropathy Spectrum Disorder Characteristics and Epidemiology Age of presentation 2 distinct age groups: – Early onset (majority of patients) neonatal insult – Some subjects develop the ANSD condition in adolescence or early adulthood. Generalized neuropathy Peripheral neuropathy Acquired (head trauma) ANSD Database: Ears Affected Bilateral: 92.9% Unilateral: 7.1% Bilateral Unilateral Multiple etiologic factors involved No true “cause” identified, though multiple risk factors are known to exist: – – – – – Perinatal factors Genetic factors Inner ear malformations CNS malformations Immune disorders Perinatal factor – CNS immaturity ELBW infants are at elevated risk for both SNHL and ANSD Compared with infants with SNHL, infants with ANSD are younger (GA 28.3 vs 32.9 weeks) and smaller (BW 1318 vs 1968 grams), with longer hospital stays (Xoinis et al, 2007) Perinatal factor – Hyperbilirubinemia Bilirubin selectively damages brainstem auditory nuclei, the auditory nerve, and spiral ganglion cells (Shapiro et al, 2001), which can undermine the temporal coding of auditory information (Shaia et al, 2005) Berlin et al (2010) noted 48.8% of 150 patients with ANSD had hyperbilirubinemia (47.7% premature, 20.3% exchange transfusion) Perinatal factor - Others Ototoxins – vancomycin, decadron Anoxia, hypoxia, cerebral palsy Intracranial hemorrhage, traumatic brain injury Mumps Genetic factors Some families with ANSD in multiple members May be syndromic or non-syndromic Many patterns of inheritance: dominant, recessive, mitochondrial, and x-linked Two main genes are presently of interest: OTOF and DFNB-59 Otoferlin (OTOF) Locus 2p23.1 Expressed in IHC, possible role in membrane trafficking and/or IHC synaptic vesicle function Nonsyndromic prelingual moderate-profound sensorineural hearing loss At least 42 pathologic mutations of OTOF known to cause this phenotype, some temperature sensitive Speech comprehension is severely impaired Pejvakin (DFNB 59) Locus 2q31.1-q31.3 Pejvakin is distributed in the cell bodies of neurons in the spiral ganglion and brainstem auditory nuclei Nonsyndromic prelingual sensorineural hearing loss Can have ANSD or non-ANSD phenotype Other genetic causes Charcot-Marie-Tooth Waardenburg syndrome Leber’s hereditary optic neuropathy Mohr-Tranebjærg syndrome Autosomal dominant optic atrophy Many other candidates Inner ear malformations Huang et al (2010) evaluated MRI scans of 103 children with ANSD All N = 103 71 (68.9%) 15 (14.6%) 11 (10.7%) 7 (6.8%) 6 (5.8%) 1 (1.0%) 12 (11.7%) 28 (27.2%) CNS malformations Huang et al (2010) evaluated MRI scans of 103 children with ANSD All N=103 66 (64.1%) 37 (35.9%) 7 (6.8%) 13 (12.6%) 19 (18.4%) 18 (17.5%) Immune disorders Guillain Barre syndrome is an autoimmune inflammatory demyelinating polyneuropathy, usually triggered by an acute infectious process – Involvement of the peripheral nervous system and has been associated with ANSD History and Risk Factors (153 pediatric patients) Normal history Normal pregnancy Premature birth Hyperbilirubinemia Exchange transfusion Anoxia Respiratory distress Artificial ventilation Ototoxic drugs Low birth weight Anemia Number (Percent) 28 (18.3%) 31 (20.3%) 73 (47.7%) 74 (48.4%) 31 (20.3%) 26 (17%) 23 (15%) 35 (22.9%) 44 (28.8%) 11 (7.2%) 6 (3.9%) Berlin, Hood, Morlet et al., 2010 Varieties of ANSD 50% of patients have no defined etiology Genetic factors: 40% Toxic-metabolic (anoxia, hyperbilirubinemia), immunological (drug reaction, demyelination), infectious disease (post viral): 10% Rare cases of head injury (children and adults) Some forms of ANSD may be progressive Some forms of ANSD may also involve OHC functions Auditory Neuropathy Spectrum Disorder Diagnosis Pathophysiology ANSD with quite similar physiological and audiological findings can occur as a consequence of: – pathology of IHC, – their synapses, – and/or the auditory nerve Middle Ear Muscle Reflexes Percent Absent MEMRs (all absent) Bilateral AN/AD Unilateral AN/AD 84.67 5.33 Total Absent 90.00 Abnormal (combination of elevated and absent) Bilateral AN/AD 8.67 Unilateral AN/AD 1.33 Total Abnormal 10.00 (number of subjects) From Berlin, Hood et al., 2010 No MEMR Some MEMR Tests Results: Efferent Neural Function Middle Ear Muscle Reflexes Stimulus Ear: Right Ipsilateral 500 Patient 1 A 2 105 3 A 4 A 5 ND 6 105 7 A 8 95 95 9 100 10 100 11 105 12 110 13 A 14 90 15 ND 1000 2000 4000 Contralateral 500 1000 2000 4000 A 105 A A ND 105 A 105 100 95 95 A 110 A 85 ND A A A A ND A A A A A A A A A ND A A ND A ND A ND A A A A ND A A ND 110 105 ND 110 100 A 110 100 A A ND 110 110 90 115 A A ND 110 A A A A A A ND A A A A A A ND A A A ND A A A ND ND A A A Absent MEMRs (all absent) 90% Abnormal (elevated/absent) 10% A 100 ND 105 110 A 110 A A A ND 110 A 85 A No MEMR Some MEMR From Berlin, Hood, Morlet et al., 2005 OAEs in ANSD OAEs are usually normal or near normal in individuals with ANSD. Absence of OAEs in ANSD: – – – – – due to a conductive issue (external and/or middle ear) ototoxic drugs (antibiotics, chemotherapy) aging, noise (hearing aid) mixed type of hearing loss due to ANSD OAE test results Percent Left Ear Present Absent Partial/Questionable 76.19 16.88 6.93 Right Ear Present Absent Partial/Questionable 75.22 15.93 8.85 From Berlin, Hood, Morlet et al., 2010 ABR and Cochlear Microphonics (CM - electrical responses generated in part by the outer hair cells) Normal ABR to condensation and rarefaction clicks; CM inverts - neural components do not. ANSD patient - all CM, no neural response Auditory Brainstem Responses Distinguish the cochlear microphonic from neural responses. The ABR is markedly abnormal in individuals with ANSD. Recordings might appear as – 1) a “flat” ABR with no evidence of any peaks or – 2) some poorly synchronized but evident later peaks (wave V) that appear only to stimuli at elevated stimulus levels (in about 25% of patients). Neural Synchrony Stimulus Envelope Single Unit Discharges Compound Action Potential Changes in neural firing patterns can account for reduced or dys-synchronous responses Single Unit Discharges Compound Action Potential Starr, 2001 Cochlear Microphonic (CM) Cochlear microphonic provides a valid measure of hair cell function. CM generally remain present in individuals with ANSD despite loss of OAEs. Appropriate identification of the CM will help in evaluating outer hair cell function in patients who have lost or never had OAEs and it will help evaluate outer hair cell function in cases of middle ear effusion when the recording of OAEs is not possible. CM can become attenuated and difficult to detect when patients are over the age of 50 years. CM in normal subjects Associated Disorders and Differential Diagnosis “What other auditory problems might ‘look like’ ANSD, based on similar test results?” Associated Disorders and Differential Diagnosis Cochlear Nerve Deficiency AI duPont Database 32 children (out of 160+) were identified with MRI evidence of cochlear nerve dysplasia (CND). Three were affected bilaterally. 60% of unilateral cases occurred on the left side. Other inner ear anomalies were found in 50% of patients including all patients with bilateral CND. The majority of these 32 patients tested had an audiometric profile of ANSD (absent MEMR, present OAEs/CM, absent ABR). Absent or hypoplastic auditory nerves are not uncommon and these cases usually resemble ANSD when OHC are present and functioning. Unilateral Auditory Neuropathy Imaging studies Imaging studies are useful in evaluating hearing loss to diagnose inner ear malformations as well as to check for presence and size of the auditory nerve. Absent or hypoplastic auditory nerves are not uncommon (Buchman et al., 2006) and these cases usually resemble ANSD when OHC are present and functioning. Audiological management in these patients is problematic because a cochlear implant cannot work when the nerve is absent and might not work well when the nerve is hypoplastic. An MRI does not give the full picture! Associated Disorders and Differential Diagnosis Cochlear Nerve Deficiency Friedreich Ataxia Friedreich Ataxia may look like ANSD Dys-synchrony Gap detection affected as well Brain still able to process language for a while (but in good conditions only, i.e., without background noise). Dys-synchrony occurs after acquisition of language (ANSD which mostly affects preverbal infants). Rance et al., 2010 Associated Disorders and Differential Diagnosis Cochlear Nerve Deficiency Friedreich Ataxia Enlarged Vestibular Aqueduct EVA: Definition EVA is the most common radiological abnormality seen in children with SNHL: 5-15% of children with SNHL have EVA. EVA can be associated with other congenital ear anomalies, such as a hypoplastic cochlea. Studies suggest that most children with EVA will develop some degree of hearing loss. SNHL onset may occur from birth to adolescence, usually during childhood and may be precipitated by various factors such as head trauma. Hearing loss is often progressive and can fluctuate. Vestibular and balance disorders can also be associated. Children with an EVA present with a wide variety of audiometric thresholds and physiologic measurements. Audiometric Pattern Agreement between EVA side and HL (60%) Agreement between different audiological tests: – – – – – OAEs ABRs MEMRs PTA Speech Bilateral EVA 125 250 500 0 20 30 R L 2 [ R ] [ 10 1 L R ] L 4 [ R ] 8 L L L R L [ R L ] 40 50 60 70 Normal MEMRs 80 90 100 110 120 Subject 037 Subject 006 Bilateral EVA, Unilateral HL 125 250 500 1 2 4 8 0 10 L 20 30 L L L L L L 40 Normal MEMR LE Absent MEMR RE 50 R 60 70 80 R R R 90 R 100 110 120 Subject 022 R R R Unilateral EVA and Bilateral HL 4/44 LE EVA Subject 015 Absent MEMRs and OAEs bilaterally Subject 030 ANSD Pattern LE EVA Subject 004 Present CM, Absent ABR ANSD Pattern LE EVA Subject 037 EVA Phenotypic expressions associated with EVA are heterogeneous to include the following possibilities: – – – – normal hearing total deafness progressive sensorineural hearing loss fluctuating sensorineural hearing loss or sudden sensorineural hearing loss, sometimes subsequent to head trauma. – There is not always agreement between OAEs, ABRs, MEMRs, PTA & speech scores. Other Candidates? Slitrk proteins control neurite outgrowth and regulate synaptic development. Slitrk6 plays a role in the survival and innervation of sensory neurons in the inner ear and vestibular apparatus. Slitrk6 Associated with cochlear dysfunction attributed to outer hair cell disease and an auditory neuropathy spectrum disorder in humans. Associated Disorders and Differential Diagnosis Cochlear Nerve Deficiency Friedreich Ataxia Enlarged Vestibular Aqueduct (Central) Auditory Processing Disorders ANSD and CAPD Different etiologies But both share similarities Can be confused unless appropriate testing is used Treatment is not the same Auditory Processing Disorders In children, auditory processing disorder (APD) presents as difficulty processing speech despite audiometrically normal hearing. Commonly, this difficulty is most pronounced in the presence of competing background noise, which, unfortunately, represents most typical real-world listening situations. The causes of (C)APD are not known, and in all likelihood, (C)APD as broadly defined represents a family of auditory processing deficits stemming from multiple causes. Clinical Presentation MEMR present and in the normal range OAE present Suppression of OAEs present Normal ABR (to a click) Normal speech in quiet Impaired speech in noise Deficits related to auditory percepts dependent in temporal cues Illustrative Case Normal birth and medical history 11 months: ENT for ear infections Babbling at 12 months 14 months: 1st set of tubes 1st true word at 18 months 22 months: 2nd set of tubes 3 years: ENT for speech delay. Failed most of her 1st grade classes Soundfield audiogram indicated normal hearing thresholds in at least the better ear. Speech therapy recommended 7 years: Audiology for CAPD evaluation Fluctuations in achievement (good/bad weeks)` APD suspected: Importance of the triage ANSD vs APD ANSD APD Normal Normal Abnormal or absent Present OAE Present or absent (over time) Present ABR Abnormal or absent Normal Normal Word recognition (quiet) Normal to severe/profound Excellent to poor Excellent Word recognition (noise) Poor Fair to poor Tympanogram MEMR Pure-tone thresholds Auditory Neuropathy Spectrum Disorder or (C)APD? Auditory Neuropathy Spectrum Disorder – ABR, MEMR absent – Cortical potentials can be present – Cochlear implants a management option Central APD – – – – Peripheral synchrony usually within normal limit ABR, MEMR usually normal Cortical potentials present Cochlear implant not useful Associated Disorders and Differential Diagnosis Cochlear Nerve Deficiency Friedreich Ataxia Enlarged Vestibular Aqueduct (Central) Auditory Processing Disorders Neuromaturation Neuromaturation Hyperbilirubinemia. Exchange Transfusion Present TEOAEs Normal thresholds by 7 months Attias and Raveh, 2007 ANSD → SNHL Some infants are diagnosed with ANSD right after birth. OAEs/CM disappear during the first few months of life Behavioral responses difficult to obtain Can be confusing for parents. Auditory Neuropathy Spectrum Disorder: Implications for Newborn Hearing Screening Goal: Screen all types of Hearing Loss Outer hair cells Inner hair cells Auditory nerve INSERM, Montpelier Promenade ‘round the cochlea Absence of Risk Factors in ANSD Some infants with ANSD have no risk factors and come through the well-baby nursery. NOT ALL infants with ANSD are found in the NICU ANSD and Newborn Hearing Screening If only OAEs are used as an initial screener, 10% of children with HL who have normal OAEs also may have serious auditory synchrony problems. Similarly, if only alternating polarity or single polarity ABR is used as an initial screener, approximately 10% of children with flat or abnormal ABRs will have normal OAEs and may misdiagnosed. Children with ANSD are currently being found more frequently because of the proliferation of newborn ABR-based hearing screening programs. Protocols for Screening in Premature Babies and Full-term Babies Percentage of preterms with ANSD is higher than in fullterm babies. Number of ANSD patients may end up being similar in both nurseries. Why would a different standard applied to identification of sensory hearing loss (all nurseries) and ANSD (NICU only)? Variation in Auditory Neuropathy Spectrum Disorder What we have learned from our databases: - Kresge Hearing Research Laboratory - Vanderbilt University - AI duPont Hospital for Children Patient Variation: A Continuum of ANSD No overt delays or auditory complaints until adulthood or until first MEMRs or ABR 1 Inconsistent auditory responses, best in quiet, poorest in noise. Audiograms can be misleading or fluctuate. ABR always desynchronized, middle-ear muscle reflexes absent. Visual phonetic language usually works best until cochlear implantation, unless family prefers cultural Deafness. 5 Total lack of sound awareness 10 Berlin, Hood, Morlet et al., 2005 Management of Auditory Neuropathy Spectrum Disorder: Detection versus Discrimination in Management and Decision-making with ANSD Wi thi nN o No rmal rm al-M Limit s od e ra te Mil M d-M od ild era Mil d -Se te Mil d-P vere rof o Mo Mo und Mo derat derat e e der ate -Seve -Pr r ofo e un Se Se d ver e-P vere rof o Pro und fou nd Degree of Pure Tone Behavioral Hearing Loss (number of ears/258) 45 40 35 30 25 20 15 10 5 0 Berlin, Hood, Morlet et al., 2009 How does it sound? Dr. F-G Zeng http://www.ucihs.uci.edu/hesp/Simulations/simulationsmain.htm Kresge ANSD Database: Speech recognition ability Subjects over 4 years of age (n=68) – Measurable word recognition in quiet only (n=25) Average maximum word recognition (Quiet): 45% Word recognition (Noise): 0% – Word recognition in quiet and in noise: n=5 100 Word Recognition (Percent Correct) – No measurable word recognition in quiet: n=38 LE RE 80 60 40 20 0 -10 QUIET 0 10 Quiet Group (n=25) 20 QUIET 30 40 NOISE 50 60 Quiet and Noise Group (n-5) From Berlin, Hood et al., 2010 Word recognition in quiet: ANSD (n=22 subjects) Note: 40 patients have 0% word recognition in quiet with hearing sensitivity ranging from mild to severe. Word recognition in quiet: SNHL Data from Yellin et al. (1989) study of patients with SNHL Word recognition in quiet: ANSD (n=22 of 62 subjects) = 40 of the 62 patients with 0% word recognition in quiet with hearing sensitivity ranging from mild to severe. The ANSD Team and Management Decisionmaking ANSD: A Team Approach Audiologic - FM; Hearing aids; Monitor behaviorally; Cochlear Implant work up based upon progress with hearing aids Medical: Otologic (ENT), Neonatology, pediatric, neurology - Medical issues, imaging ANSD: A Team Approach Speech-Language: expressive and receptive assessments; communication mode - Re-evaluate every 3 months to verify 3 months progress in 3 months time - Yes; continue to evaluate every 3 months - No; initiate cochlear implant work up and continue monitoring progress Communication Methods Language Development – Is critical; work closely with speech/language pathologists, early interventionists, educators Visual Communication – Methods such as Cued speech, sign language, signed English are important to facilitate language development. Auditory Verbal Therapy – Without visual information, before cochlear implantation, has not worked in our practice as the sole method of teaching language. ANSD: A Team Approach Psychological/Developmental/Parent/Family Counseling (Social Worker): learning abilities, family stress indicators, cochlear implant and communication expectations Early Intervention Educational Contacts (Deaf Educator/Special Education Director): school programs available, address academic and communication needs The audiogram cannot be the driving force in management The ABRs and audiogram do not provide the clinician with information as to the severity of hearing impairment. The pure tone thresholds give indication as to the patients’ level of sound awareness but do not reflect the severity of the patients’ problem with auditory timing. Several patients would never have been considered as implant candidates based on the audiogram alone. ANSD management with FM systems ANSD patients generally have very poor ability to understand speech in background noise. Benefit demonstrated with FM systems, particularly for patients with residual speech understanding in quiet Efferent feedback function (middle-ear and olivocochlear reflexes) is disabled Thought to assist in listening in noise (e.g., Liberman and Guinan, 1998) Kresge Hearing Lab ANSD Database: Amplification Variable benefit from hearing aids – Based on data from 85 patients Good benefit (functional interaction) 4% Some benefit (helpful in language acquisition) 8% Little benefit (environmental sounds) 26% No benefit 62% From Berlin, Hood, Morlet et al. (2010) AI duPont Database: Hearing Aid Trials: 86 patients out of 134 Hearing Aid Benefit (86 patients) Three Sites: 198 Hearing Aid Users Kresge Lab ANSD Database Cochlear Implant Outcomes All Kresge database patients Percent Successful Too soon to tell (recent CI) Insufficient information 77.78 14.82 7.41 Only patients seen at Kresge Lab Successful Too soon to tell (recent CI) Insufficient information 82.35 11.76 5.88 Based on 49 patients with ANSD From Berlin, Hood, Morlet et al. (2010) AI duPont: 31 Cochlear Implants Three Sites: 99 Cochlear Implant Patients Factors that may help in predicting outcomes and management Understanding risk factors; possible markers for delayed neuromaturation Separating pre- and post dendritic responses From Santarelli et al., 2008 – e.g., Santarelli, Gibson, McMahon, et al. Cortical responses and speech perception From Rance et al., 2002 Cortical Potentials Normal maturation and functioning of auditory cortical areas is a precondition for normal development of speech and oral language skills. Disruption of normal maturational processes will result in diminished capacity for speech/language acquisition. Cortical potentials are useful in assessing maturation and function of the auditory cortical areas. Cortical Potentials: P1 latency Sharma et al., 2011 ANSD: Issues and Challenges Distinguishing detection of sound and discrimination of sound in management planning – Isolating cochlear, synaptic, neural function Genetics of AN/AD, imaging, cochlear nerve agenesis, EVA • Predicting who will develop speech/language with little intervention • Specific risk factors • Protocols for recommending and fitting hearing aids, FM systems, cochlear implants Resources Listserve for parents and professionals interested in ANSD [email protected] Our Website for information and links: www.kresgelab.com Links to our email addresses and lab websites Contributions to our database are welcome. Colleagues at Kresge Hearing Research Laboratory and the Audiology Clinic, Department of Otolaryngology, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA Charles I. Berlin, PhD Linda J. Hood, PhD Jill Bordelon, MCD Leah Goforth-Barter, MS Jennifer Taylor-Jeanfreau, MCD Li Li, MD Kelly Rose Mattingly, MA Sonya Tedesco, MCD Han Wen, MSBE Harriet Berlin, MS Shanda Brashears, AuD Annette Hurley Larmieu, PhD Bronya Keats, PhD Elizabeth Montgomery, MS Patti St. John, MCD Melanie Thibodeaux, MCD Diane Wilensky, MS The Hood Lab at Vanderbilt University: Lindsey Rentmeester AuD, Kelsey Hatton BS, Susan Stangl BA, Heather McCaslin AuD, Christopher Spankovich AuD PhD, Andrea Hillock AuD PhD Vanderbilt University AI duPont Hospital for Children: Ashleigh l. Greenwood, AuD Research supported by the NIH-NIDCD, Oberkotter Foundation, Deafness Research Foundation, American Hearing Research Foundation, National Organization for Hearing Research, Marriott Foundation, Kam’s Fund for Hearing Research, Vanderbilt University Development Funds