R(I) 6/02

Mr. J. M. Henty	CI/4567/1999
11.12.00
Prescribed disease A10 (occupational deafness) – types of audiometry test
The claimant was found to have met the conditions of entitlement to disablement benefit for prescribed disease A10, having had her hearing loss tested by pure tone audiometry. On re-assessment the results of a further test by the same method were thought to be unreliable, so a Cortical Evoked Response audiogram was obtained. That produced lower results for the claimant’s loss of hearing, and benefit was refused. The claimant obtained a Brainstem Evoked Response audiogram supporting her claim, and appealed to a tribunal. The tribunal considered the Cortical Evoked Response audiogram to represent the claimant’s true hearing level and dismissed the appeal. The claimant appealed to the Commissioner.
Held, dismissing the appeal, that:
	the tribunal were entitled to prefer the results of the Cortical Evoked Response test, they gave proper reasons and findings, and their decision on the facts was not irrational or perverse.
[Note: The Commissioner obtained and considered expert evidence relating to tests by pure tone audiometry, and two types of Electric Response Audiometry (Cortical Evoked Response, also known as Vertex Response, and Brainstem Evoked Response).]

DECISION OF THE SOCIAL SECURITY COMMISSIONER

1.	This is an application for leave to appeal. Both parties have consented to my treating the application for leave as the substantive appeal, pursuant to regulation 11(3) of the Social Security Commissioners (Procedure) Regulations 1999 and, accordingly, I do so. I grant leave to appeal.

2.	At the request of the claimant, I held an oral hearing in London, which is the normal venue in England, at which Mr. Sangha of Messrs. Murria, solicitors, lucidly presented the case for the claimant, and Mr. Chang of the DSS Solicitor’s Department appeared for the Secretary of State. I am grateful to them both for their assistance in this difficult case. The appeal is not supported.

3.	My decision is that the MAT was not erroneous in point of law. The appeal is, therefore, dismissed.

4.	Before considering the details of this case, I must emphasise that a Commissioner sits in an appellate jurisdiction and there is an appeal to him only on a point of law. Broadly speaking a tribunal errs in law if (1) it adopts an incorrect proposition of law; or (2) there has been a breach of the rules of natural justice; or (3) the decision is supported by no evidence; or (4) the decision is irrational or perverse within “Wednesbury Principles”; or (5) the tribunal has given inadequate reasons.

5.	The claimant was for 15 or 16 years employed as an operator of a variety of metal working machines, such as are identified in the column marked “Occupation” in Part I of Schedule 1 to the Social Security (Prescribed Diseases) Regulations 1985, and she became deaf. She made a claim for disablement benefit for occupational deafness (PD A10) on 6 February 1991. 

	(i)	She was seen by an audiometric technician who completed a report on 24 March 1992 (page 16), as a result of which the AMA, on 12 May 1992 (12-15), decided that there was a hearing loss of 56 dB in each ear, on the prescribed averages. The AMA awarded benefit at 30% disablement until 5 February 1996. That test appears to be a test based on Pure Tone audiometry – as to which see below.

	(ii)	For the purposes of re-assessment an audiometric technician saw her again on 19 January 1996 and conducted another test on the Pure Tone basis. The overall hearing loss appeared to average 93 dB in the right ear and 95 in the left.

	(iii)	That was thought unreliable – it certainly seemed to call for further explanation – and accordingly a Cortical Response Evoked audiogram – as to which see below – was obtained on 20 May 1996 (22-23) from Professor Harding. That measured a hearing loss of 50 dB in the right ear and 43 in the left.

	(iv)	Accordingly, the claimant did not satisfy the test for PD A10 and, as a result, the AMA, having examined her on 27 June 1996, re-assessed disablement at “less than 20%” from 6 February 1996 to 5 February 2001, provisional. Benefit was accordingly withdrawn.

	(v)	The claimant appealed, and submitted, in support of her appeal, a report dated 1 October 1997 (32-34) by Mr. McCrae Moore, a consultant ENT surgeon. He conducted a Brainstem Evoked Response Audiogram – see below – and concluded there was an overall loss of at least 50% in each ear.

6.	The appeal first came before a MAT on 15 September 1998. They adjourned, because of a need for clarification of the reports before the tribunal. Mr. McCrae Moore was to be asked to specify the confusion from the markings on the audiogram of 20 May 1996 (which was the audiogram conducted by Professor Harding) and Professor Harding would then be asked to respond. In fact, no comments were received from Professor Harding, or at least none appears in the papers.

7.	Mr. McCrae Moore did respond in his letter of 26 January 1999 (38A – B). He appreciated that there were two different markings on the audiogram at 500 Hz on the left at 50 and 60 decibels and 3 different markings of hearing levels at 2000 Hz on the left at 40, 50 and 60. He added that the lesser of these markings had been taken as an accurate reading, and, even if those markings were accepted, that would limit the claimant’s hearing to a maximum of 50 decibels on both sides with a slight increase to 40 decibels at 2000 Hz on the left. However, it seems to me that the tribunal, in fact, answered this apparent confusion by setting out what the Cortical Evoked Response Audiogram, which the claimant had underwent, entailed. I will return to this later.

8.	The tribunal sat for the substantive appeal on 11 February 1999, when they dismissed it. That tribunal was differently constituted from that which sat on 15 September 1998. It has been suggested on the claimant’s behalf that there was, thereby, a breach of the rules of natural justice. I do not need much persuasion in rejecting that submission. There is no rule that the constitution of a tribunal has to be identical on each occasion the tribunal sits on an appeal, although if the constitution of a later one is in fact different – as it was in this case – the hearing has to be a complete re-hearing of the appeal. If the rule were otherwise, manifestly great difficulty would be encountered in getting together the same members. 

9.	Now I was at a loss to understand the various different tests which have been mentioned and, on 6 April 2000, I raised a direction asking for assistance in this respect. The Secretary of State obtained a most useful and informative report from Dr. Susan M. Reed BSc, MB, ChB Dip Occ Med dated 7 June 2000, which I have no doubt is both authoritative and impartial (58-72).

She describes pure tone audiometry thus:

	“A pure tone (i.e. it is a single frequence not many frequencies) stimulus is presented to each ear through the earphones for approximately a second until the threshold of hearing (i.e. the minimum intensity of noise necessary to be audible) is acknowledged in at least 50 per cent of presentations. ...

	The test requires a response from the patient, e.g. by pressing a button when they hear the sound i.e. it is a subjective test. Provided the patient is co-operative, PTA is a very good method of assessing hearing. However, PTA is a subjective test as a voluntary conditioned response is required by a patient to an acoustic stimulus. Various factors including extrinsic and intrinsic variables affect the reliability and accuracy of this test. ...”

It must be emphasised that the test is a subjective test.

Dr. Reed then considers Electric Response Audiometry (ERA) for objective assessment. She states (64 et seq.):

	“It may be necessary to establish objective evidence of normal hearing or hearing loss in cases where conventional testing is inappropriate e.g. young children with multiple handicaps suspected of hearing loss; or where it is suspected that the PTA does not reflect the true hearing loss, e.g. due to the response to conversational voice suggesting a better level of hearing than the PTA shows; or those where accurate thresholds need to be established, e.g. in cases of litigation (noise induced deafness).

	Electric Response Audiometry (ERA) is a well established method for the objective assessment of hearing acuity in patients who are unable or unwilling to perform the subjective tests i.e. PTA.

	ERA is itself is an umbrella term covering a variety of different responses ...”

ERA is an objective test.

Dr. Reed then – as indeed asked in my direction – considers two types of Electric Response Audiometry. 

She first describes Brainstem Evoked Response.

	“This is often used in paediatric populations since this response is resistant to anaesthetic and sedative agents. The brainstem is the base of the brain just above the spinal cord. It is the part of the brain which controls such things as taste, and hearing.”

She then describes Cortical Evoked Response.

	“The most appropriate test in adults is the Cortical Evoked Response Audiogram (CERA) also known as the Vertex Response (SVR). (The cortex is the surface of the brain). This test essentially assesses the integrity of the entire auditory system and consequently is expected to have a high degree of validity for estimating thresholds. For this test, short duration tones, similar to those used in PTA are used to elicit a response. Therefore, the major advantage of this test for medico-legal assessment is that it is possible to produce an objective audiogram, assessing the loss of each frequency for AC and BC, not relying on the reliability of the individual as in conventional audiometric assessments.

	This test can therefore indicate whether an individual’s hearing loss is genuine or not and if not can give an estimate of the true auditory threshold.”

10.	There are two peripheral points which I shall deal with first.

	(i)	In his report (23), Mr. McCrae Moore says that, while there was a history of TB suffered by the claimant, there was no history of treatment with e.g. streptomycin, which can cause hearing loss. The tribunal closely questioned the claimant about the injections she had when she was suffering from TB, and, as to this, they said:

			“It appears that she has had streptomycin given her as part of the treatment for her TB in 1965. The type of streptomycin given at that time for treatment of TB was not one which produced deafness but it did produce vestibular effects of tinnitus but we can eliminate streptomycin as being a cause of her overall hearing loss ...”

		I see nothing wrong with that. Evidently, they concluded from the questioning that the claimant had, in fact, had streptomycin but, even if that were so, the form of streptomycin given to her would not have caused deafness. That they, therefore, ruled out as a cause of the claimant’s deafness. I can see no possible criticism of the tribunal in this regard.

	(ii)	There is then the question of causation as to which they said 

			“ ... we feel that with the low frequency loss and the flat type of trace there is some other constitutional loss causing her hearing deficit other than noise.”

In view of what I have decided in this appeal, this does not strictly arise, but, if it did, I would want a very strong argument why I should hold that the reasoning of the tribunal was deficient in this respect.

11.	As to the substantive question I am not going to beat about the bush. The tribunal said:

	“The Evoked Response Audiometry is the one we consider to be the most likely audiogram of all of them to represent on the balance of probabilities the true level of hearing [the claimant] has.”

The reference is in fact to the Cortical Evoked Response, and audiogram, which was carried out by Professor Harding, was carried out according to that method. This appears clearly from the tribunal’s reasons. The test conducted by Mr. McCrae Moore was the Brainstem Evoked Response. In their expert opinion, the tribunal considered the Cortical Evoked Response Audiogram the test ‘to be the most likely audiogram of all of them to represent on the balance of probabilities the true level of hearing’. The PTA was clearly not appropriate, having, to some extent, lost credibility by the surprising readings from the test of 16 January 1996. The tribunal, therefore, preferred the test conducted by Professor Harding. That is a view which is not irrational or perverse and one which they were entitled to hold. It is not a decision in which, therefore, I can interfere. Furthermore, I am reassured in this conclusion by what Dr. Reed herself had to say, which I have quoted at length above, when she herself said it was the most appropriate test for adults.

The confusion that there may have been in the markings on the audiogram of 20 May 1996 is due to the mechanics of how the Cortical Audiogram works. The tribunal have explained this and identified the misunderstanding. Finally they say:

	“Further tests were done at lower intensities and are marked as dots on the Evoked Response Audiogram and this represents hearing appreciation on the electro-encephalogram at either 1 or 2 occasions but not all 3 occasions and therefore this is not taken into account in compiling the audiometric patterns of the Evoked Response Audiogram. This fact has not been sufficiently appreciated by Mr. Moore’s letter dated 26 January 1999.”

That being so there is, in my view, no deficiency in the tribunal’s judgment. Proper reasons and findings have been given. The fact that Professor Harding was not asked to comment any further is immaterial, since the tribunal have provided the explanation themselves.

12.	That being so my decision is as set out above. The appeal is dismissed.

Date: 11 December 2000					       (signed) J. M. Henty
Commissioner