When Stroke Affects the Temporal Lobe
The temporal lobe is one of four lobes that make up the cerebral cortex, the wrinkly hemispheres of the brain right beneath the skull. The temporal lobe (TL) is about the size of a fist and extends from the temples to just behind the ears on both sides about half way up the skull. Its blood supply comes from the middle and posterior cerebral arteries.
Dr. Chris Anderson
“The left and right temporal lobes are connected through the corpus callosum, which is the fiber tract that joins both hemispheres together,” said Chris Anderson, M.D., MMSc., associate director, Acute Stroke Service, Center for Genomic Medicine at Massachusetts General Hospital. “They don’t wrap around to join each other, but they certainly talk to each other a lot, through the corpus callosum and the thalamus as well.”
The TL has several functions, mainly involved with memory, perception and language. Being so close to the ears, the left and right TLs process what we hear. The TL is involved in attaching meaning to language. It plays a role in auditory, visual and long-term memory. The optic nerves pass through it on their way to the occipital lobes at the back of the brain, where vision is processed. The left TL includes Wernicke’s area, which spans the region between the temporal and parietal lobes, and plays a key role in speech comprehension.
The TL’s main blood supply is from the middle cerebral artery. “That is a big artery so it supplies a lot of the temporal lobe but also a lot of the frontal lobe and even the parietal lobe,” said Anderson. Because of that, an ischemic stroke in the TL often involves injury to other parts of the brain. A hemorrhagic stroke is different. “Subarachnoid hemorrhages can happen that are pretty strikingly restricted to the temporal lobe. But also, intracranial and intracerebral hemorrhage can cause very specific lesions localized within the temporal lobe and cause deficits only within it.”
These are symptoms associated with temporal lobe strokes:
- Difficulty recognizing common sounds or where they are coming from, like where to look for a dog that you hear barking;
- Difficulty interpreting multiple sounds when they occur simultaneously, like understanding a person in a noisy environment;
- Difficulty with depth perception, inability to see objects in a portion of visual space (in both eyes, like visual field cuts);
- Difficulty comprehending speech;
- Difficulty accessing old memories, difficulty remembering things that occurred long ago;
- Personality changes, changes in mood or energy level;
- Changes in sexual desire or sexual behavior.
Emotions and Behavior
Lesions in the TL can also affect the limbic system, which is a complicated network that both stimulates, as well as inhibits, different emotions. If the inside surface of the TL (known as the mesial TL) is damaged where it interacts with the limbic system, “it affects how survivors process their emotions and react to emotional stimuli,” Anderson said. “People with problems in their mesial temporal lobe can have fits of rage, inappropriate crying or laughing [pseudobulbar affect], even things like lassitude or apathy, meaning that they don’t react to anything. Typically, these things require damage to both temporal lobes but even with damage to one, people can notice differences in the way that they process emotions.”
Stroke affects each brain differently. “It is hard to predict what will happen. A stroke in the same location can cause one person to become angry and another person to be laissez-faire or happy-go-lucky or sort of flaccid,” Anderson said. The same is true for sexuality: “Some patients would become essentially asexual after one particular lesion in the temporal lobe while another may become hypersexual.” Anderson cautions that the frontal lobe is essentially responsible for how people react. “In other words, if your temporal lobe is making you relatively hypersexual but you have a very strong inhibitory frontal lobe, you may not act on those impulses.”
The TL plays an important role in processing both auditory and visual perception. Although vision is not processed in the TL, the optic nerves pass through it on their way to the occipital lobe. “Think of the temporal lobe as part of the highway that connects our eyes to the part of the brain that makes sense of what our eyes see,” Anderson said. A stroke in the TL can affect those impulses, called optic radiations, and create visual field cuts.
Language is processed in the TL, particularly in the left TL, where Wernicke’s area is located. “That is an area of the brain that’s important for helping us attach meanings to words that we hear, as well as produce new language,” Anderson said. “A stroke that affects the temporal lobe in Wernicke’s area will leave a person with aphasia. Overall, there’s much more likelihood of having language deficits after a temporal lobe stroke on the left than on the right.”
A stroke in the TL can also affect memory because of how close the TL is to the hippocampus. “We have two hippocampi, which are small regions on the very inside of the temporal lobe,” Anderson said. “They are responsible for laying down long-term memories. If both are lost, as sometimes happened in old-time epilepsy surgeries, then no new memories are created, and the person will meet you for the first time every day. If only one is injured by a stroke, the circuits may get scrambled a little bit, but typically the other hippocampus is still functioning fine, and it can pick up the slack as things go forward.”
Anderson identified the most common deficits from TL strokes as visual field problems and language problems. Both of these respond well to therapy. With vision, occupational therapists generally focus on compensatory therapy, like learning scanning techniques if there is a field cut, because it is not possible to restore vision that is lost.
“In the language area, there’s a lot that can be done therapeutically through speech and language therapy to improve a survivor’s ability to understand as well as produce language, speech and writing,” he said. “It’s one of those things that if you don’t rehabilitate it, it takes much longer to come back and it doesn’t come back as strong. It doesn’t mean we can get people back to normal; most of the time we can’t. But we certainly can get them to as high a level of function as their bodies will let us.”
He relates this somewhat to the TL’s plasticity, but also to the fact that there are two of them. “I think a lot of the plasticity and a lot of the recovery you see after stroke in terms of language recovery has to do with the ability of the temporal lobe to wire to the other side,” he said. “There is substantial plasticity there for recovery, and patients who’ve had a stroke within the temporal lobe should feel like there is still a substantial potential for them to have a good recovery.”
Carissa Kauwell of Mount Joy, Pennsylvania, had a stroke the day after her 40TH birthday as the result of a carotid artery dissection compounded by two different clotting disorders. The ischemic stroke was described in her discharge documents as a “left frontal, temporal, parietal CVA,” and it left her with deficits in auditory perception and language comprehension, including aphasia.
Immediately post-stroke, her condition was described as moderate global aphasia. “In my records, it says that I refused to stick out my tongue or do this and that,” she said. “But I didn’t refuse, I just didn’t understand what they were saying. I could speak without any slur or anything like that, but I had a very difficult time finding words and expressing myself. I couldn’t read or really write. So, I definitely had global aphasia at the time.”
Today, three years after the stroke, she has made substantial recovery, but the remnants of her aphasia and auditory problems still dog her every day, especially at work. She is training for a new job with the postal service, and language comprehension is a challenge. “Probably half of what they’re telling me I can understand. If it’s something like technical instructions, questions, numbers, that type of thing is very difficult for me to understand,” she said. “If we’re just chit-chatting one-on-one, that’s easy. But if it’s over the phone, if someone has an accent, if they mumble, I have a hard time understanding.”
Numbers are a particular problem as is someone speaking fast: “It’s like there’s a disconnect in my brain. If I’m with my family or if I’m at a store with too much background noise, it’s almost impossible to understand someone speaking to me, because my brain hears everything around me, and I can’t focus on what the person is saying. It’s sensory overload.”
She never drives with the radio on because of that. “My brain just gets tired. If I’m driving after work, I just need quiet to decompress and focus on driving.”
She feels her personality has changed because other people have commented on that. A long time friend described her as acting like a child and an older person, too. Her aphasia is an ongoing challenge: “A lot of times when I deal with people and I don’t understand what’s being said, especially in a parent-child conference or job interviews, those types of professional instances, I feel embarrassed.”
Carissa had six weeks of speech therapy about six weeks after her stroke. “My therapist focused on my writing and made me read aloud,” she said. “I don’t think she really understood my deficits with auditory comprehension. Through my own research, I learned about the ‘auditory comprehension’ diagnosis. When I read it, I said, ‘So, that’s what it’s called.’”
Approaching the three-year anniversary of her stroke, she doesn’t feel that her auditory comprehension has really improved much while the rest of her issues have improved a lot. She would like to get some therapy for auditory comprehension.
In the past three years, she has progressed emotionally to a point of acceptance, even making peace with the inconvenience of warfarin, which treats her clotting disorders. “Part of me just feels like this is the way I’m going to be for the rest of my life and I’m just grateful to be alive and feel lucky I’ve gotten as good as I am compared to a lot of people that have strokes and aphasia. I’m able to express myself both verbally and through writing. But like I said, sometimes I feel embarrassed and wish I could get my brain back to what it was. But this is how it is, and you just have to deal with what you have and do the best that you can with it.
“When you’ve had a stroke, it’s almost like someone has died, and you have to go through the stages of grief and get to a point where you accept ‘This is the way I am now’ and move on. Over the past three years I’ve noticed that I still improve sometimes, but I’m okay with who I am now. I really am.”
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