Leukemia, a cancer that begins in the blood-forming tissues, has the potential to affect the auditory system. This complication can arise from the disease process itself or as a side effect of the treatments used to fight the cancer. The connection between leukemia and hearing loss is complex, involving mechanical disruptions caused by abnormal blood cells and cellular damage from therapeutic agents. Understanding how hearing is impacted is important for early diagnosis and management.
How Leukemia Directly Impacts Hearing
The disease itself can cause hearing loss through pathological mechanisms that interfere with the structures of the inner and middle ear. One direct cause is leukemic infiltration, where cancerous white blood cells migrate and accumulate in other tissues. These cells can invade the temporal bone, which houses the inner and middle ear, or directly infiltrate the cochlea, the organ responsible for hearing. This presence of abnormal cells can disrupt normal function or lead to inflammation.
Another mechanism involves the hyperviscosity syndrome, a complication of certain leukemias, particularly those with very high white blood cell counts (hyperleukocytosis). The excessive number of white blood cells thickens the blood. This highly viscous blood struggles to flow efficiently through the microcirculation of the inner ear, which is supplied by the labyrinthine artery. The resulting sluggish blood flow and potential for microclot formation (leukostasis) can cause an infarction or lack of oxygen to the cochlear tissues.
This microvascular obstruction and tissue damage often result in sensorineural hearing loss, caused by damage to the inner ear or the nerve pathways to the brain. Hearing loss directly caused by the disease may appear suddenly and can sometimes be the first symptom leading to a leukemia diagnosis. In some cases, the presence of leukemic cells or resulting hemorrhage in the middle ear can lead to a mixed hearing loss, which includes sensorineural and conductive components.
Hearing Loss as a Side Effect of Leukemia Treatment
While leukemia itself can affect hearing, the most frequent cause of auditory complications is chemotherapy, a side effect known as ototoxicity. Chemotherapeutic agents, designed to eliminate cancer cells, can also damage the healthy cells of the inner ear. This damage primarily targets the cochlear hair cells, which convert sound vibrations into electrical signals the brain can interpret.
Among the agents used in leukemia protocols, platinum-based drugs like cisplatin are the most notorious for causing ototoxicity. Cisplatin damages the outer hair cells in the cochlea, often starting at the base, which detects high-frequency sounds. The severity of the hearing loss is dose-dependent; the higher the cumulative dose received, the greater the risk of permanent damage.
Other therapies, such as high-dose methotrexate and cranial radiation, are also recognized as ototoxic agents. High-dose methotrexate can directly damage the cochlea. Radiation therapy to the head and neck region can cause hearing loss if the temporal bone is included in the treatment field. The resulting hearing loss is usually bilateral and permanent, often presenting as a high-frequency sensorineural hearing loss. Patients may first notice difficulty hearing speech in noisy environments or experience tinnitus (a persistent ringing or buzzing sound).
The risk of ototoxicity is higher in children than in adults because their developing auditory systems are more susceptible to damage. In pediatric patients receiving cisplatin-based therapy, the incidence of hearing loss can be as high as 60% to 100%. Even after treatment concludes, the hearing loss can sometimes be delayed or progressive, requiring long-term monitoring for survivors. Early identification and management are important parts of survivorship care.
Screening and Managing Auditory Complications
Given the risk of ototoxicity from treatment, a proactive approach to screening and monitoring is essential for all leukemia patients. The process begins with a baseline audiological evaluation performed before the start of any treatment involving ototoxic agents. This initial testing provides a clear picture of the patient’s hearing status against which subsequent tests can be compared.
The standard diagnostic tool for monitoring is pure-tone audiometry, which measures hearing thresholds across various frequencies. Because chemotherapy-induced hearing loss frequently affects the higher frequencies first, audiometric testing includes frequencies up to 8,000 Hertz (Hz) or higher to detect subtle changes early. Auditory monitoring is performed frequently during treatment, especially before each new cycle of ototoxic medication, and continues for years after treatment ends, particularly for pediatric patients.
If hearing loss is detected, management and intervention strategies can be implemented. For patients with sensorineural hearing loss, the primary intervention is often hearing aids, custom-fitted to address the specific pattern of loss. In cases of profound hearing loss, a cochlear implant may be considered to restore functional hearing.
Preventive measures are also an area of research and clinical practice. One otoprotective agent is sodium thiosulfate, which reduces the incidence and severity of cisplatin-induced hearing loss in children with non-metastatic cancer. In cases where leukemic infiltration or hyperviscosity is the cause, aggressive treatment of the underlying leukemia, such as leukapheresis to rapidly reduce the white blood cell count, may reverse the hearing loss if performed early enough.