Inflamed in the brain

It’s spring in Toronto and I’ve just returned from a conference where I spent several days surviving almost entirely on coffee, adrenaline, and much less than my usual 8 hours sleep. Somewhere between the flight home and unpacking my suitcase, I notice something feels odd about my left hand.

At first, it’s subtle. My fingertips feel slightly numb, as though I’ve slept on my arm or have been sat awkwardly at my desk in my home office. But over the next few days the sensation begins creeping upward from my fingers, to forearm and then up my arm to my shoulder and beginning to spread across my chest, like somebody slowly turning down the volume on my sensory nervous system.

Then I realise I can no longer properly feel temperature through that hand. I hold it under running tap water in my bathroom and although I understand that the water is cold, but the sensation itself feels lukewarm, strangely muffled and incorrect. My brain and body no longer seem to agree on reality.

Now, despite being a neuroscientist, my first instinct is not “Ah yes, this appears to be a demyelinating neurological disorder.” My first instinct is more along the lines of “That seems… potentially bad.” But also I have to repeatedly demonstrate this lack of sensation to Ben, by showing him how I can hold an ice cube without feeling pain and touch a scalding hot cup of coffee without wincing.

After a brief and deeply unhelpful period of Googling symptoms, during which the internet helpfully suggests everything from vitamin B deficiency to cardiac arrest, I take myself to Toronto Western Hospital Emergency Department. The triage nurse asks why I’m there. “My arm and hand have gone sort of numb,” I say, attempting to sound calm and medically literate rather than like somebody about to spiral psychologically in a waiting room.

Once it’s established that I’m probably not actively having a heart attack, I spend the next several hours being examined by an ever-rotating cast of doctors armed with pins, reflex hammers and lollipop sticks. “Does this feel sharp?” “What about this?” “Can you feel this equally on both sides?” “Close your eyes.” “Push against my hand.”

At some point a neurologist gently says the phrase “We’re going to get you in the MRI.”

This turns out to be one of those sentences that instantly changes the emotional atmosphere of your entire life. By midnight I’m lying in a hospital bed on the neurology ward wearing an oversized blue gown, staring at off while ceiling panels while trying to convince myself that everything is probably fine. Maybe I’ve slipped a disc in my spine - that’s fixable. Maybe I’ve trapped a nerve - I’m sure that’s also fixable. Except somewhere underneath the rational scientist part of my brain, another quieter voice already knows that something is not fine and the 7am MRI confirms it.

Multiple sclerosis. An autoimmune disease where the immune system mistakenly attacks myelin, the fatty protective coating surrounding nerve fibres in the brain and spinal cord. Inflammation damages the efficiency of neural communication, almost like stripping insulation from electrical wiring. I insist on looking at the scans with the neurologist who oblige and flexes his medical knowledge as I begin bombarding him with questions. The lesions on the MRI appear as small bright scars scattered throughout my brain, and one active one lies in my spinal cord at the C2/C3 level, fingered to be causing the sudden flare of my symptoms. Evidence that my immune system has been shredding my nervous system like a bored labrador retriever who has ripped up a couch because it hasn’t been walked for several days.

I’m immediately put on an IV of a fast-acting corticosteroid to firehose the inflammation and issued a prescription to continue with an extraordinarily high dose of prednisone to extinguish my immune system.

After I was discharged, I walked back to my west end apartment through the green lushness of Trinity Bellwoods park. One of the strangest things about receiving a neurological diagnosis is suddenly realising that your thoughts, emotions, memories and physical sensations all emerge from fragile biological tissue that can become inflamed, damaged and disrupted.

As a neuroscientist, I would often speak about the brain in abstract terms cognition, memory, identity, consciousness. Then one day you are staring at images of the damage inflicted by your own body inside your own nervous system. Immune cells. Chemical signals. Activated microglia. Cytokines. White blood cells sneaking through biological barriers they ideally should not be crossing.

The sort of inflammation capable of changing not only how your body feels, but how you think, remember, focus and emotionally experience the world itself.

Your Brain Has an Immune System

For a long time, scientists believed the brain was largely protected from the immune system. The brain was considered “immune privileged” and therefore isolated from the inflammatory skirmishes occurring elsewhere in the body. And in some ways, this made sense. The brain is delicate and needs to control essential life preserving activities, like breathing.

Neurons generally cannot be casually replaced like skin cells so any kind of excessive inflammation inside the skull would be catastrophic. So, the brain evolved protective mechanisms like the blood-brain barrier.

The blood-brain barrier is exactly what it sounds like: a tightly regulated biological border separating circulating blood from the central nervous system. You can imagine it as an extremely selective nightclub bouncer standing outside the brain. Water? Glucose? Oxygen? Absolutely come on in. Random toxins and inflammatory chaos? Not tonight buddies.

This barrier is composed of tightly packed cells lining blood vessels in the brain, helping regulate what substances gain access to neural tissue.

Without it, the brain would essentially stew in every inflammatory fluctuation happening throughout the body. Unfortunately, the relationship between the brain and immune system turns out to be far less isolated than scientists once believed. The brain does indeed have an immune system. And when that system becomes activated, things can get strange.

If neurons are the glamorous celebrities of neuroscience, microglia are the exhausted backstage crew cleaning up broken glass after the concert. Microglia are specialised immune cells that live within the brain and spinal cord. Their job is to patrol the nervous system looking for problems in the form of infections, dead or dying cells or other threats.

When functioning normally, microglia are essential housekeepers. They remove debris, help shape neural circuits and support healthy brain development. They even mop up a few stray toxins while they are on patrol.

But when activated excessively or chronically, microglia can become inflammatory little arsonists. Activated microglia release inflammatory chemicals called cytokines. Cytokines are signalling molecules used by the immune system to coordinate inflammatory responses. Some cytokines are useful and protective. If you catch a virus, for example, inflammatory cytokines help mobilise the immune response needed to fight infection. But the problem arises when inflammatory signalling becomes chronic.

Think about the last time you had influenza. Not a mild sniffle, real influenza. The kind where your body feels as though it has been beaten with rocks and you can’t stop sweating even though you feel cold. Aside from the chills and aches, you also likely experienced exhaustion, low mood, reduced motivation, social withdrawal, poor concentration, no appetite and emotional flatness.

Interestingly, many of these symptoms overlap substantially with depression.

For years, scientists assumed these changes occurred simply because sick people felt physically unwell. But it turns out the immune system actively communicates with the brain during illness. Inflammatory cytokines help generate what researchers call “sickness behaviour”, which is an evolutionarily adaptive behavioural state encouraging rest and recovery.

From a survival perspective, this makes sense as if your immune system is busy fighting infection, sprinting around hunting wild elk or attending networking events is probably not ideal. The brain shifts priorities. Energy conservation becomes more important than ambition. Social withdrawal reduces pathogen spread and fatigue forces rest. And importantly, the brain often cannot distinguish particularly well between acute inflammation and chronic low-grade inflammation.

One of the most interesting developments in modern psychiatry is the growing recognition that inflammation may contribute to mental health symptoms in at least some individuals. This does not mean depression is “just inflammation”. Human psychology is vastly more complicated than that. But mounting evidence suggests inflammatory processes may influence mood, cognition and behaviour.

People with elevated inflammatory markers are statistically more likely to experience depression. Individuals with inflammatory autoimmune conditions such as rheumatoid arthritis, lupus, inflammatory bowel disease and multiple sclerosis often show higher rates of depression and fatigue, not just because of pain and symptoms of the diseases, but because of the inflammation itself. Administration of inflammatory medications can induce depressive symptoms. And importantly, some people with depression exhibit elevated inflammatory cytokines.

This has led researchers to propose inflammatory subtypes of depression. The overlap becomes particularly striking when considering symptoms like fatigue, reduced motivation, cognitive dysfunction, emotional numbness and social withdrawal. These are not merely emotional experiences. They are also biological states.

The Brain on Fire

One of the strange emotional experiences of being diagnosed with a neurological disease is suddenly realising your brain is not some abstract philosophical concept. It is fragile biological tissue. Before being diagnosed with multiple sclerosis, I suspect some part of me still viewed the brain romantically as the seat of consciousness, intellect and personality.

Then one day you are sitting in a medical imaging centre staring at MRI scans containing literal inflammatory lesions inside your central nervous system that damages communication between neurons. And suddenly the brain becomes horrifyingly physical.

Depending on lesion burden, location and the connections impacted, symptoms may include numbness, weakness, emotional changes, balance, neuropathic pain, visual disturbances, cognitive dysfunction, crushing fatigue and temperature sensitivity. I asked for my brain scan files with some intention of analysing my grey matter volume (yes, I am that kind of nerd). But instead, I would stare at my brain scans at home, wondering if the scar in my left temporal lobe was a cause of the depressive episode I experienced in December 2020 while the COVID-19 virus ran rampant globally. Or the ghostlike smear in my cerebellum made me terrible at balancing on one leg during yoga. Or the tiny intensity in my right parietal lobe was the culprit when left side of my face felt like it had an aesthetic block for 3 weeks when I was travelling around Japan in 2008. I asked my neurologist about this and was told that it’s basically impossible to determine whether a specific MS lesion causes a symptom. However, there have been studies linking anxiety to white matter lesion burden the connective region between the temporal lobe (which contains the amygdala and hippocampus) to frontal cortex regions. You bet I scrutinize my MRI scan when I read the paper… But regardless, my brain contains a battleground of scars.

One of the most disorienting aspects of neurological illness is the invisibility. You can look outwardly functional while internally feeling as though your nervous system has been plugged into faulty electrical wiring. For weeks after I had the flare leading to my diagnosis, I walked around feeling like I had sunburn down my arm, a manifestation of neuropathic pain from the damage to my myelin. But outwardly the skin on my arm appeared completely normal, no physical indication of the prickly heat and redness I could feel.

Moreover, true neurological fatigue is unlike ordinary tiredness. This is kind of fatigue where your thoughts feel physically heavy, like trying to solve a crossword but the questions are all written in a secret code and just trying to read feels overwhelming. Inflammation changes the texture of consciousness itself.

“Brain fog” is one of those terms scientists historically hated because it sounded annoyingly imprecise. And admittedly, it does sound slightly like a Dungeons and Dragons attack card. But as somebody who has both researched cognition and personally experienced inflammatory neurological disease, I think dismissing brain fog is a mistake because people know when their thinking changes.

Brain fog is difficult to define neatly because it encompasses multiple cognitive experiences like slowed thinking, reduced attention, forgetfulness, difficulty finding words and feeling detached from your own thoughts

Inflammation appears capable of contributing to many of these symptoms as cytokines can influence neurotransmitter systems, alter energy metabolism. Moreover, they affect neuroplasticity and interfere with communication between brain regions. And importantly, the brain itself is metabolically expensive. Thinking requires energy.

An inflamed brain is not an efficient brain.

Stress and Fire

One of the cruel ironies of modern life is that psychological stress also influences inflammatory activity. The brain and immune system are deeply interconnected.

Chronic stress alters cortisol signalling, immune regulation, sleep quality, metabolic function and inflammatory tone. Acute stress is adaptive. If you are being chased by a bear, temporary stress activation is useful. But humans now experience many stressors that are chronic, psychological and inescapably abstract. Finances. Emails. Job insecurity. A boss that treats you like a fool. Relationship instability. Social comparison. Doomscrolling the news.

The body responds to chronic psychological stress as though danger remains permanently present.

And chronic stress can amplify inflammatory processes. Inflammation can worsen mood and poor mood can worsen stress. Stress can worsen eating behaviours or reignite old addictions or habits. Poor diet can further increase inflammation. Modern humans can become trapped inside self-perpetuating biological loops.

Diets high in ultra-processed foods are associated with increased inflammatory activity. Several mechanisms likely contribute such as excessive refined sugar, trans fats, altered gut microbiota, metabolic dysfunction, oxidative stress, obesity-associated inflammation and insufficient fibre intake.

Importantly, fat tissue itself is not metabolically passive. Adipose tissue can release inflammatory cytokines. As obesity progresses, inflammatory signalling often increases. Again though, this conversation must be handled carefully. Bodies are complex and a person’s weight alone is not a moral failing. And inflammation can occur across a spectrum of body sizes. But the modern food environment appears capable of shifting the body towards a more inflammatory state. And the brain notices.

Food, Autoimmunity and Hope

One of the more intriguing developments in nutrition research is the growing evidence that dietary patterns may influence autoimmune and inflammatory diseases — including conditions like multiple sclerosis. After my diagnosis one of the first things that showed up was the Wahl’s diet protocol, devised by Dr Terry Wahls, a physician who herself was diagnosed with multiple sclerosis and advocates a modified Paleo-style diet that eliminates specific dietary components such as gluten, casein, and lectins along with removing sugar, dairy products and eggs.

However, despite my deep knowledge of nutrition and neuroscience, food is not a magical cure-all. Autoimmune diseases are extraordinarily complex. Genetics. Immune dysfunction. Hormones. Infections. Stress. Environmental toxin exposures. Plain bad luck. And autoimmune diseases are increasingly common, estimated to affect approximately 5% to 10% of the global population, with prevalence rates rising by about 12.5% annually. They represent the third most common category of chronic illness worldwide, following cancer and cardiovascular diseases.

But increasingly, research suggests that diets dominated by ultra-processed foods may worsen inflammatory signalling in the body, while dietary patterns centred around minimally processed, fibre-rich foods may help support immune regulation and reduce inflammatory burden in at least some individuals.

Emerging evidence in multiple sclerosis is particularly interesting. Recent studies have found that people with MS who consume higher amounts of ultra-processed foods tend to show greater inflammatory disease activity, more relapses and more active lesions on MRI scans over time. I repeat myself this when I eat a kale salad or pour blueberries on my Greek yogurt.

Researchers suspect the confluence of increased inflammatory cytokines, disruption of the gut microbiome, impaired gut barrier integrity, oxidative stress, changes in immune cell activity can stoke the fire of inflammation throughout the body. In other words, the immune system appears highly responsive to the broader metabolic environment we create through lifestyle.

This does not mean people with autoimmune diseases caused their illness by eating the wrong things. That narrative is both scientifically inaccurate and emotionally cruel.

But it does suggest that reducing ultra-processed foods may help lower some of the inflammatory “background noise” the immune system is operating within.

And honestly, this aligns with my own experience.

After my MS diagnosis, I more interested in one simple question “How can I help my brain and nervous system feel as supported as possible?” Because when you live with neurological inflammation, you become acutely aware that cognition, mood, energy and physical sensation are not separate systems. They are deeply linked biological processes.

For me, eating feels more like an act of nervous system maintenance than wellness culture. I sincerely believe that we only live once, so I am not going to deny myself simple pleasures like a glass of crisp New Zealand Sauvignon Blanc in the garden with my friends on a summer evening, or sharing a dessert with my husband on a date night.

Importantly, research also suggests that inflammatory changes can respond relatively quickly to dietary shifts. Studies examining diets lower in ultra-processed foods have demonstrated improvements in inflammatory markers and gut microbiome composition within weeks. This is not about dietary perfection, it is about recognising that the brain is not isolated from the immune system, and the immune system is not isolated from the environments we repeatedly expose it to — including food.

What the Brain Remembers

One thing chronic illness teaches you very quickly is that health is not simply the absence of disease. Health is energy. Clarity. Mental flexibility. The ability to think sharply enough to feel like yourself. When inflammation interferes with cognition, people often describe feeling disconnected from who they used to be.

And because these changes are frequently invisible, they are often minimised. “You’re just stressed.” “Everybody gets tired.” “You probably just need to sleep more.” Sometimes that is true, but sometimes the immune system has chomped on your myelin and now your nervous system’s wiring resembles that of a run down house.

What fascinates me most is that modern lifestyles appear capable of nudging many people towards low-grade inflammatory states without them fully recognising it. Sleep deprivation. Sedentary behaviour. Ultra-processed diets. Chronic stress. Social isolation. Environmental pollution.

The brain absorbs all of it. And eventually, the whole body keeps score. Not only in arteries or waistlines. But in mood. In memory. In cognition. In the texture of thought itself.