The powerful drugs in chemotherapy destroy cancerous cells, but they also damage normal tissue. Some chemotherapy patients experience direct or indirect damage to the central nervous system and the cranial nerves, according to the American Cancer Society (ACS). The central nervous system contains the brain and spinal cord; the cranial nerves are directly connected to the brain and are responsible for relaying information to other parts of the body. The effects of chemotherapy on the brain can begin immediately or years after treatment.
"Chemo Brain"
One of the effects of chemotherapy on the brain is "chemo brain," according to the ACS. Also known as "chemo-fog," it refers to the cognitive impairment that some chemotherapy patients exhibit, which can continue years after the treatment has ended. The Mayo Clinic states that "chemo brain," impacts short-term memory, verbal memory and visual memory. Patients also have confusion, difficulty concentrating, mental fogginess and a short attention span. Other symptoms of "chemo brain" include becoming unusually disorganized, problems finding the right word, difficulty learning new skills, fatigue and problems multitasking.
Cranial Nerve Damage
Twelve cranial nerves are connected to the human brain, which relay motor and sensory messages to the rest of the body. Chemotherapy can damage these cranial nerves, interfering with the signals being sent from the brain. The ACS states that vision is affected, with symptoms included blurred vision and double vision. Hearing problems are another group of symptoms, such as hearing loss and tinnitus (ringing in the ear). Other cranial nerve damage from chemotherapy symptoms are dry mouth and an increased sensitivity to odors.
Additional Central Nervous System Damage
The ACS notes that damage to the brain from chemotherapy can disrupt normal activity in the brain, resulting in seizures. Some patients may feel lethargic, nausea and vomiting, which are common side effects of chemotherapy. Other symptoms include depression, headaches, stiff neck and fever.
