Chiari Malformation (CM) is a disorder characterized by an anatomical deformation at the base of the skull, cerebellar tonsillar herniation, or brainstem herniation via the foramen of magnum and up to the cervical spinal canal. 1 Cleland was the first to discover Chiari malformation in 1883. This condition was defined as an extension in the appearance of a wedge of cerebellar tonsils and the medial portion of the inferior cerebellum lobules that went throughout the medulla within the cervical canal as a result of cerebral hydrocephalus ². CM is categorized into five subtypes (Type 0 – IV) Type 0- Hydrodynamic changes of (CSF) Syringomyelia with or without tonsillar herniation, Type I- Caudal cerebellar tonsillar herniation greater than 5 mm, Type II - Caudal herniation of the cerebellar vermis, brainstem, and 4th ventricle through the foramen magnum, accompanied by hydrosyringomyelia, myelomeningocele, and hydrocephalus. There can be additional intracranial abnormalities (tentorium hypoplasia, craniolacunia, Sylvian aqueduct anomalies), Type III- Occipital encephalocele with intracranial abnormalities associated with Chiari II, Type IV- Cerebellum aplasia or hypoplasia along with tentorium cerebelli aplasia ³. Among these, Type I is certainly the most frequent, except in early childhood, where type II is more common ⁴. This ailment may be asymptomatic and detected by chance during an imaging study. The most prevalent symptom is occipital and neck ache that worsens with physical activity or Valsalva maneuvers. There is a loss of superficial abdominal reflexes, radicular ache, and hand dysesthesias ⁵. An oto-neurological examination reported sensorineural hearing loss, vertigo, nystagmus, disequilibrium, tinnitus, facial hypesthesia, dysphagia, and vocal cord paralysis ⁶. A study that evaluated the case histories of 130 patients with the Chiari malformation, reported that auditory vestibular symptoms were common (in 22% of cases) and also stated that the incidence of bilateral sensori neural hearing loss was commonly compared to unilateral ⁷. The study assessed three individuals who reported having asymmetric sensorineural hearing loss. Arnold-Chiari type 1 malformation was detected by magnetic resonance imaging. All three patients showed progressive hearing loss ⁸. According to a study, nine individuals with Chiari Malformation-I, two of whom were men and seven of whom were women, had an average age of 42.8 years. One patient had rapid hearing loss, two instances had recurrent vertigo with peripheral characteristics, five patients had Ménière-like disease, and one patient had sensorineural hearing loss that began in early childhood. The most frequently described audio-vestibular symptom in the literature is unsteadiness (49%), which is followed by hearing loss (15%), nystagmus (15%), and dizziness (18%). Nystagmus is frequently horizontal (74%), or down-beating (18%). Hyperacusis (1%), auditory fullness (10%), and tinnitus (11%) are further audio-vestibular symptoms ¹. The prevalence of audiovestibular symptoms and the progressivity of the condition demands detailed audiological assessment. Thus, the present case report highlights the Audiological and Subjective vestibular evaluation findings and the importance of the test battery approach in individuals with Chiari malformation associated with communicating hydrocephalus.

A 36-year-old female came to the department with the complaint of reduced hearing sensitivity along with ringing sensation and not being able to understand speech in the noisy condition in the left ear for 2 years. She also reported that 2-3 episodes of vertigo along with Nausea, imbalance while walking, and severe headache every month for 2 years. Detailed history noted the nature of the hearing loss was progressive and medical history reported a known case of Chiari-1 malformation associated with mild communicating hydrocephalus confirmed by an imaging study (Magnetic Resonance Imaging (MRI). She was under medication for vertigo and headache for the past 1.5 years. Following the history and findings of the MRI, a detailed audiological evaluation was carried out using a battery of tests in order to assess the extent of involvement of auditory and vestibular systems.

The detailed neurological evaluation including Magnetic resonance imaging revealed the presence of Chiari type 1 malformation (Table 1) The pattern of hearing loss and the nature of vestibular deficits are still underreported in the literature. Reported symptoms are tinnitus, impaired hearing ⁹, positional vertigo and nystagmus ¹⁰. This case shows the patient to have had episodic vertigo with tinnitus and hearing loss for 2 years before she consulted for a medical opinion.

Like reported in literature, CM type I is often seen in adults compared to other types of Chiari Malformation 10 and the present case is also adult female with reported onset of symptoms in the past 2yrs. Fluctuating type of hearing loss as in Meniere’s disease is often reported 10 11. Same was seen in this patient as well. Complaints of difficulty in hearing in noise and subjective vestibular evaluation to be indicative of central origin should alert the audiologist for possible central pathology ⁸.

Detailed audiological evaluation was carried out in this case. Pure tone average and speech recognition scores (SRS) report normal hearing sensitivity in the right ear with 100% WRS and severe-profound hearing loss with 5% in the counterpart (Table 2). Both unilateral SN losses and bilateral losses are reported ¹² Mixed components are not reported in literature, but this case presents a significant AB gap on PTA with masking. Mixed components are often reported in cochlear extension of acoustic nerve tumors. Subjective vestibular tests (Table 3) were carried out which indicated the presence of nystagmus (horizontal type) in the spontaneous nystagmus test and the patient deviated more than 30 degrees towards the left while performing the Fukuda stepping test and also showed instability and swaying during sharpened Romberg test which confirms the presence of vestibular impairment ¹. Though prolonged wave III and V are reported on ABR findings for CM ¹², the same could not be assessed in the present case, due to severity of hearing loss.

The current case report's findings, which include unilateral severe to profound hearing loss and tinnitus matched to 3kHz, and Diagonal pattern acoustic reflexes, hearing loss of recent onset, necessitate a neuro-otological evaluation because they indicate the possibility of both peripheral and central mechanism involvement. The patient in this instance, however, had previously had a neurological assessment and had been diagnosed with type 1 chairi malformation. According to studies, hearing loss can occur over several months or years. But in this case, the patient provided a two-year history. The degree of hearing loss was also found to be associated with the severity of current issues ⁷. Among the potential causes of hearing loss and balance problems in patients with Chiari malformation are the following: the cerebellar tonsils directly compress the brainstem nuclei, the congenitally elongated eighth cranial nerve is stretched as the brain stem shifts caudally, and the eighth cranial nerve is compressed along the bony surface of porous acusticus as it descends to caudally depressed nuclei 7. Furthermore, it is recognized that most disease entities that induce hydrocephalus also cause hearing loss through different processes. However, an independent link between CSF dynamics and hearing has been attributed to fluid pressure communication between CSF, perilymph, and endolymph. endolymphatic sac transmits cerebrospinal fluid (CSF) pressure changes to the endolymph to equalize CSF pressure changes transmitted to the perilymph via the cochlear aqueduct. Relative endolymphatic hydrops can result from perilymphatic hypotension caused by low cisternal CSF pressure. Cisternal CSF hypertension can also result in relative perilymphatic hydrops ⁹. Thus, the present case report supports the evidence-based practice and highlights the need for detailed audiological and vestibular evaluation in individuals with Chiari-1 malformation associated with communicating hydrocephalus. Audiological tests can detect severity of the condition and progressivity. Often management choice is surgical, but time of surgery may be decided by surgeons based on severity of the symptoms and rate of progress of the condition. Auditory-vestibular investigations may help in this decision making process.

This case report highlights the outcomes of an audiological evaluation and subjective vestibular evaluation in an adult female with Chiari-1 malformation and hydrocephalus. Hearing loss and balance difficulties can be progressive, so audiological and vestibular evaluations are vital to understanding pathophysiology, seeking the appropriate therapeutic approach, and enhancing the overall quality of life in these patients.