Editor’s Note: We are indeed most fortunate to have the venerable Dr. Shivashankar, from Bangalore, India, share some of his vast clinical experience in NeuroAudiology with the readers of Pathways. This month we will present part 1 followed by part 2 next month.
I take immense pleasure in sharing my clinical experiences with you through this note. Most of what I have spoken about here is from my experience at the National Institute of Mental Health and Neurosciences (NIMHANS), an Institute of National Importance under the Ministry of Health and Family Welfare, Govt. of India (https://nimhans.ac.in/).
I worked at this institute for close to 38 years prior to my retirement. I saw the department grow and I take great pride in saying that it has earned a name for excellence in audiology, particularly in the field of neuro-audiology. The institute has a dedicated and well-established department of Speech Pathology and Audiology (https://nimhans.ac.in/speech-pathology-and-audiology/).
The institution has over 25 departments working towards the welfare of patients with neurological and psychiatric disorders. Multi-disciplinary work is the backbone of clinical care in this institution. I have chosen four cases that I feel will help unravel the importance of clinical history, observation and diagnostic work-up. I hope you enjoy reading the case presentations in commentary form.
Case history – the key arrow in the audiologist’s armamentarium
In our practice in India and perhaps globally too, we never miss an opportunity to stress on the importance of the process of taking case history. Indeed, taking a good history is the first and the most important step in patient care. In my experience case history forms evolve over time and evolve with experience of the treating team. Case history forms vary from set up to set up and is usually formulated keeping the patient population in mind.
A case history form contains a series of pre-laid printed questions that are asked one after the other before embarking upon audiological testing. Although it is a set of known questions, the way you ask these questions is an art. An art that gets better over time and with practice. Students in India and particularly students who are trained under me, at both, undergraduate and graduate levels, are trained thoroughly to understand the art of collecting history. In addition to the pre-set questions, I strongly recommend that there is a space at the very end of the case history form that gives the clinician a chance to document details pertaining to key observations a clinician made while taking detailed history. This will not only help decide further steps for audiological evaluations but provide a good starting point for the mentor/supervisor to provide the roadmap/pathway for next steps in the assessment and rehabilitation process. You will notice that I come back to the point around good history taking throughout the narrative that follows.
All this said, there are other things an audiologist needs to possess – for example the set up you work for, will force you to dive deeper into a particular area. An audiologist working in a neurosciences hospital will have to upgrade skills in neuro-audiology. Whereas, an audiologist working in an otology set up, limited to middle ear surgery, may have to learn audiology skills pertaining to that set-up. Once you dive into a subject deeper, there is no end to learning. But what gives me the most happiness is exploring the art of differential diagnosis. This is one more thing that I will bring up multiple times in the paragraphs that follow.
Before I go onto narrating a few cases, I would like to re-iterate that case history coupled with sound knowledge of the auditory system, ability to judiciously use audiological evaluations having an inquisitive mind, and qualities of kindness, passion and so on, will help you walk through the maze of diagnostic audiology with ease and joy.
Case A: Chikku taught me the importance of inquiry
It was in the beginning of my career when I was sailing in an unchartered ship with very basic knowledge in my field that I encountered a child with an audiogram depicting severe sensory-neural hearing loss. I was working in a multi-speciality hospital in the department of Otorhinolaryngology (ENT). This was prior to my appointment at NIMHANS where I served the rest of my career. It is a story about a very smart and adorable 7-year-old boy called Chikku (name changed)
.Chikku walking on his toes, entered my poorly lit room with his mother. He stood at the corner of my table and started jumping with an inviting smile. Although he was not speaking age adequately, he was communicating complex ideas with gestures combined with minimal verbal output. His mother, who seemed very distressed, handed over the child’s audiogram sheet and said, ‘the doctor has referred him to you for a hearing aid’. Though I was listening to what the mother was telling me, I was closely drawn towards the child’s behaviour – why did he toe-walk? Why was he jumping? Why was he restless? I felt he had ADHD, but there was something more. I was curious! How did the ‘doctor’ get an audiogram within such a short period given his behaviour? I also noticed that the audiogram was plotted by a technician (an experienced one) and not an audiologist. This was reason enough for me to question the validity of the audiogram and conclusions drawn by the ENT team. I began to dive deeper into the history
I asked Chikku’s mother if there was a seasonal effect on the hearing abilities that he displayed. This question was not in the case history sheet. But my intuition forced me to ask this question. Surprised by this question, Chikku’s mom said ‘Yes! he seems to have more difficulty in hearing in winter than in summer. She then said, I often finding him rubbing his ears. This prompted me to test his middle ear status using a middle ear measuring equipment (impedance audiometer). This equipment was under my custody as I was the only Audiologist in the department who was allowed to use this. The department also entrusted me with the responsibilities of fitting hearing aids. Tympanometry showed bilateral ‘B’ type tympanograms indicating presence of fluid in both ears (glue ears). I then took it upon myself to re-do the hearing assessment which lasted for five sessions. This included conditioning the child for the task. The test revealed bilateral conductive hearing loss.
Convincing his treating doctor about the presence of conductive pathology in the boy was an arduous task for me. With the consent of the mother (who was convinced by my approach), the child was subjected to an explorative tympanotomy in both ears. Soon after the procedure, the doctor quipped me with a remark saying ‘Hey! you are 50% wrong as we did not see fluid in one ear’. He also asked me ‘explain why we found fluid in one ear only, when tympanometry showed bilateral fluid’. The answer was very straight forward. I started by saying why not say ‘instead of 50% wrong I was at least 50% right’! I then said the reason for fluid in one ear and not in the other could be the effect of positive pressure built by general anaesthesia (GA). It is likely that GA forcibly opened the Eustachian tube that made way for the fluid to flow out or at least aeriated the middle ear. With appreciation from the doctor I returned to my seat only to witness the joy of the mother.
If I had not treaded this path which involved facing the ENTs, convincing them to consider a tympanotomy, Chikku would have been fitted with hearing aids bilaterally. Not only would this have hampered Chikku’s hearing, but it would have been a huge burden of Chikku’s family to finance his hearing aids. From this child, I learned what an audiologist should do as against what an audiology technician does.
Take home messages:
- Questions that we ask during initial contact may be out-of-the box. But, if you feel a burning need to ask a different question – ask it, as long as it is ethical.
- Observe the child – the child’s behaviour is the key to successful evaluations.
- Believe in yourself as a clinician, as an audiologist. You can make a difference to the decisions the medical team takes if you show confidence.
Case B – Central auditory processing disorder
The case report that follows, highlights the importance of audiological investigations and the application of clinical knowledge. This child was referred to me from the department of Neurology, NIMHANS, to review audiological results done in the home state of the child (center ‘X’) when the child was 5years 6 months. The audiology report from the home state showed misarticulation with severe sensorineural hearing loss in the right ear and moderate sensorineural hearing loss in the left ear (Table 1). Further the child was fitted with a behind the ear (BTE) hearing aid which the child had refused to use.
Table1: Auditory profile of the case B established at a center X:
|Impression||Severe SN loss||Moderate SN loss|
|Diagnosis||Hearing loss with Misarticulation|
|Recommendation||BTE hearing aid to the Right ear|
PTA: Pure tone average of 500, 1000 & 2000 Hz in dB nHL; SRT: Speech recognition threshold in dB nHL; ASR: Acoustic Stapedius Reflex; BTE: Behind the ear
When I saw this boy, he was six- year old (6 months since his first evaluation at center ‘X’). Primary concerns included, poor auditory responses associated with impaired hearing that lasted for approximately 8 months duration and verbal output had regressed.
The part that caught my attention was – loss or regression of verbal output in a child who had developed normal speech and language functions. Regression of verbal abilities in the absence of regression in social skills and other developmental domains made me think harder. Is this child’s audiology evaluation valid? How did previous clinicians even get an audiogram reliably? What could be causing this patten of regression? The neurologist at NIMHANS was heading towards a likely diagnosis of Landau-Kleffner syndrome (LKS). The neurologist was also concerned with the presence of acquired hearing loss.
I suspected the child’s inability to understand speech efficiently was due to an inefficient central auditory processing system and it was not because of the hearing loss as diagnosed earlier. I repeated all evaluations and like I had guessed, pure tone audiometry thresholds could not be established. However, I could track his thresholds up to 30 dB nHL based on auditory brain stem responses in both ears suggesting bilaterally normal hearing (Table 2). I also opted for auditory middle latency response (AMLR) recording to understand the functional integrity at subcortical and cortical levels. The AMLR showed normal Middle Latency Response (MLR) in both ears at 90 dB nHL (Right Pa – 28.96 m.sec and the Left Pa – 30.72 m.sec). His monotic digit score was fairly good in both ears (Rt-95%; Lt-85. %). Both tasks were presented at 70 dB HL. I had to cautiously look at these scores given the child’s age at the time of testing. I suspected central auditory processing dysfunction (CAPD) since the monotic scores were fairly good compared with the dichotic scores (42 %and 18 % respectively).
This child was finally diagnosed as having LKS by the neurology team. CAPD is often the first symptom in children with LKS. The onset of language disturbances may be abrupt or insidious in nature. Often, a classical symptom of LKS is unresponsiveness to verbal stimuli. This demonstrates impaired auditory verbal comprehension. This is usually mistaken for acquired deafness. Initially, parents are concerned that their child is becoming deaf to speech although the child is able to hear and stay alert to environmental sounds. Audiometric assessment and auditory brainstem responses are invariably normal.
It was unfortunate that this child was fitted with a hearing aid. I spent many sessions with the family explaining the condition. I referred the child and family to an audiologist and speech-language pathologist in their home state, for intervention.
Table 2: ABR latencies at 90 dB & 30 dB nHL in both ears (Case B)
|Ear & Stimulus level (dB nHL)||Absolute peak latency in m. sec.||Inter-peak latency in m. sec.|
What did this patient teach me?
- Correlating symptoms and the test results is key to arriving at a diagnostic formulation
- It is possible that the behavioral audiometric thresholds may have been influenced (made worse) by involvement of the central auditory system. This would be consistent with the essentially normal ABR.
- As audiologists we need to have working knowledge of what a neurology work-up comprises.
- It was a little surprising that the MLR was essentially normal given the involvement of auditory cortex often seen in LKS.
Dr. N. Shivashankar
Professor and Head (retired)
Department of Speech Pathology and Audiology
The National Institute of Mental Health and Neuro-Sciences