Dear Doctor: As a fan of the TV show "Homeland," I was skeptical (and also creeped out) when a character was assassinated by someone hacking his pacemaker. But I just read that this might actually be possible. My dad has a pacemaker, and now I'm worried. Is this really a serious risk?

Dear Reader: We remember when that scene aired and the resulting stir that it caused, and we admit that we share your discomfort. The idea that an unseen individual can take control of a medical device in someone else's body is profoundly disturbing. And while it would be great to be able to brush it all off as the product of a TV writer's overheated imagination, the possibility of such hacking, while remote, does exist.

A paper recently published in the Journal of the American College of Cardiology tackled this very subject, which is perhaps how it came to your attention. The authors point out that, in a world increasingly dependent on (and connected by) online technology, it's not only pacemakers that are vulnerable. Defibrillators, neurostimulators and implantable drug pumps, like insulin pumps, rely on the same embedded computers and software radios for their two-way communication. Their findings are that weak security features have left these devices potentially vulnerable to outside manipulation.

The possibility of this type of interference first arose about a decade ago. That's when technological advances made it possible to program and communicate with a pacemaker wirelessly. Up until that time, a patient had to visit the cardiologist's office for the doctor to collect data from the device, and to deliver any updates. As soon as things went wireless, that meant there was software involved. And the nature of software, as we see every day, is that it can be hacked. In addition to concerns about attacks on the functioning of various implanted medical devices, experts warn that the highly sensitive data those devices collect from patients and send out to health care providers can be compromised as well.

The Food and Drug Administration and the Department of Homeland Security have both become involved in the issue. The FDA has published a cybersecurity update on its website and outlined the steps it is taking to protect the public. Earlier this year, DHS put out an advisory regarding potential vulnerabilities in a certain cardiac device, which caused the company to evaluate and address the issue.

Unfortunately, the only foolproof fix to reduce the risk of hacking is to ditch the wireless technology. But considering the many benefits of remote access, which facilitates software updates, allows real-time monitoring and can deliver updates to treatment protocols without the physician physically present, it's realistic to expect that wireless tech is here to stay.

In addition to addressing the vulnerabilities in wireless medical technologies, the lead author has been careful to state, both in the paper and in subsequent media interviews, that the risk of such hacking remains theoretical. Here in the real world, at this point in time, there have been no documented cases of implantable cardiac devices being hacked.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Hello again, dear readers -- and happy spring!

We closed a past column with a question about how any health-related New Year's resolutions were going, whether there was success or stagnation, and what plans people had in place to move forward. And because of the focus on diet, weight loss and general health in the responses we received, we've put several columns about these topics into the pipeline, with more to come. We hope you'll find them useful.

And now, from the mailbox:

-- We always learn from your letters, and this time it's food scientist Bob Hutkins from the University of Nebraska-Lincoln who helped out. Writing about the finer points of kefir production, he explained that it's actually an added enzyme, lactase, that works the magic of making kefir lactose-free. The enzyme turns lactose into a different type of sugar, and thus allows those who are lactose-intolerant to enjoy the benefits of kefir without gastrointestinal discomfort.

-- In response to the column about ocular migraines, we heard from Kurt in nearby Thousand Oaks, California. Although Kurt experienced the visual disturbances of an ocular migraine, a brain scan led to a different diagnosis:

"The cause of the vision loss was TIAs from microemboli," he wrote. A TIA, or transient ischemic attack, is a temporary blockage of blood flow to the brain. In Kurt's case, tiny particles, which can often be blood clots, caused the blockage.

"Upon initiation of low-dose aspirin therapy, the visual symptoms immediately resolved," he wrote. "Although migraine is a serious condition, it is not life-threatening in contrast to the possible outcome of TIAs. I would encourage you to inform readers of other possible causes of transient vision loss and the need to have a thorough workup to diagnose."

-- The recent changes to blood pressure guidelines prompted more than a few of you to write, both in confusion and frustration. We agree that it can be unnerving when the same blood pressure reading that was considered normal one day is classified as elevated the next.

At this time, a reading of less than 120/80 is the new normal. A top (systolic pressure) number between 120 and 129 is now considered 'elevated' blood pressure. When the bottom (diastolic pressure) number exceeds 80, and the top number is 130 or greater, the results are considered high blood pressure.

If it's any consolation, the updated blood pressure guidelines have caused quite a bit of conversation in the medical world, and no small amount of controversy. The reason given for the changes is to promote increased vigilance by physicians and patients in dealing with high blood pressure before it causes harm.

-- To the reader who is worried that his newly diagnosed prostate cancer might be contagious, please be reassured that it is not. We quote no lesser authority than the American Cancer Society when we say there is no evidence that close contact of any type can result in the spread of cancer from one person to another.

As ever, thank you for your letters. We are grateful for your interest in this column and realize how fortunate we are to have readers like you.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I have recently experienced severe vertigo due to fluid pressing against my eardrum, which happened after a sinus infection. What was going on? How can I avoid a repeat?

Dear Reader: What you're describing falls into a collection of conditions known as otitis media, a somewhat general term that refers to inflammation of the middle ear. This is the small, air-filled chamber behind the ear drum where the tiny vibrating bones that are a crucial part of our hearing apparatus are located. Otitis media can develop any time something prevents fluid in the area from draining. Congestion arising from a cold, the flu, allergies or a respiratory infection can all lead to inflammation of the middle ear.

There are several types of otitis media. When an infection develops, this is known as acute otitis media, or AOM. The cause is most often viral or bacterial. Symptoms include pain in one or both ears, a feeling of fullness in the affected ear, muffled hearing, a sore throat or drainage from the ear. In some cases, AOM can progress into a condition known as chronic suppurative otitis media. Characterized by the persistent discharge of fluid from the middle ear through a rupture in the ear drum, this is a serious condition that can lead to hearing loss.

When fluid collects in the middle ear but is not infected, this is known as otitis media with effusion, which means fluid. As with acute otitis media, there is often a feeling of fullness in the ear, and a loss of hearing acuity. In some cases, the condition can cause the dizziness and vertigo that you described. Unlike AOM, however, symptoms typically don't include pain or fever. Acute otitis media with effusion can last anywhere from a few weeks to several months. If the condition persists beyond three months, or if it recurs, the diagnosis becomes chronic otitis media with effusion.

The culprit here is the Eustachian tube, a narrow passage between the middle ear and the rear of the nose, near the soft palate. Its functions are to equalize air pressure between the middle ear and pressure outside of the body, and to drain fluids from within the ear. But upper respiratory tract infections can cause the Eustachian tubes to become congested, which means fluids will remain trapped in the middle ear. Children's Eustachian tubes are narrower than those in adults, which is why they account for the lion's share -- at least 80 percent -- of otitis media diagnoses.

When it comes to prevention, the options are somewhat limited. It's a good idea to take a decongestant before you fly, so your ears have a better shot at equalizing pressure. When you have a cold, be sure to blow your nose gently so as not to inadvertently overcome the pressure differential of the Eustachian tubes and thus force mucus in the wrong direction. In that same vein, never hold or close off your nose when you sneeze.

Finally, other conditions can have symptoms that are very similar to otitis media. With your complaint of extreme vertigo, we think it's important to see your family doctor for a definitive diagnosis.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)