Covid -19 and the Brain

Following on from my post “Brain Fog” I thought I would write about what we know so far with regards to Covid -19 infection and the brain.

During my acute Covid -19 I developed an acute loss of smell and taste. I had phantosmia, an olfactory hallucination, of cigarette smoke and fires burning. I also had a metallic taste in my mouth. Nine months down the line I am still unable to taste subtle things like lime in a soda, I can’t smell certain things like herbs from my garden. I can have violent reactions to smells, parosmia, such as Bach’ s flower remedies pastilles which bring on overwhelming nausea.

Fortunately I didn’t suffer from any of the more severe neurological consequences of a Covid- 19 infection like so many others. That said, it wouldn’t surprise me, with my initial acute confusion and subsequent brain fog and cognitive dysfunction, if I did have a mild encephalitis - inflammation of the brain? I will never know.

The neurological manifestations of a Covid-19 infection can be broadly divided into two categories; those that occur during the acute phase of the infection (parainfectious) and the post-viral manifestations.

1. Parainfectious complications:

ANOSMIA - the inability to smell, is the earliest and most common manifestation. Nearly 60% of patients develop loss of smell and 90% have an alteration of smell. The loss of taste is thought to be secondary to the loss of smell. This can lead to reduced appetite and weight loss.

Most patients recover their sense of smell, others develop parosmia or permanent anosmia. The virus thought to invade the support cells close to the olfactory nerve endings in the nasal mucosa which express the SARS-CoV-2 receptor ACE2.

ENCEPHALOPATHY - is the most common neurological manifestation in hospitalized patients (30%). It ranges from alteration in consciousness to delirium and seizures. Its cause is complex and may be due to the significant pulmonary disease or multiorgan involvement causing low oxygen levels or metabolic abnormalities.

The SARS-CoV-2 virus is not especially neurotropic (brain infecting) such as polio or rabies. It has very limited invasion of any neural cells but it has been found on autopsies though in low viral numbers. However they do show a large invasion by immune cells particularly macrophages and lymphocytes around the perivascular regions and parenchyma regions. This was particularly prominent in the olfactory (smelling) system and the brainstem (autonomic function).

DELIRIUM-an acute confusional state, in hospitalised COVID-19 patients is common (84%). It is typically associated with sepsis and is a combination of acute attention, awareness, and cognition disturbances. It also often occurs as a result of ITU medication and/ or prolonged isolation.

STROKES - occur in nearly 1-5% of hospitalized patients with COVID-19. Patients often develop a hypercoagulable (thick blood) state with raised d-dimer levels. If untreated, they may develop arterial or venous blockages which can occur in multiple blood vessels at the same time. Haemorrhagic ( bleeding) strokes can also occur. Some develop microhaemorrhages likely due to invasion of the vascular endothelium by the virus.

2. Post-viral complications:

Following the acute phase a variety of immune mediated syndromes can occur which can affect the brain, spinal cord or peripheral nerves. These have been described with other viral infections. Acute disseminated encephalomyelitis has been reported with multifocal inflammatory lesions in the brain, spinal cord and optic nerve. Guillain-Barre syndrome, a rapid onset muscle weakness, can occur. These syndromes have autoantibodies and they respond to immunotherapies. Rare cases of acute Parkinsonism, Myasthenia Gravis and CJD has been reported.

Long Covid:

Nearly 10-35% patients continue to complain of persistent symptoms some of which are neurologic in nature. Often these symptoms can manifest after the acute phase of the illness. The severity of the acute phase does not predict the development of this syndrome either. Long Covid patients of all ages are reporting lingering neurological symptoms after COVID-19 infection.

Such as brain fog and cognitive difficulties, memory loss, persistent headaches, debilitating fatigue, loss of taste or smell, muscle pain and weakness, nerve damage, neuropathic pain. There have been new diagnoses of epilepsy

The manifestations are very similar to myalgic encephalomyelitis ME /chronic fatigue syndrome CFS.

There is also increasing evidence of autonomic dysfunction in the form of POTS which can include palpitations, or tachycardia upon mild exercise or standing, hypotension, hypertension, constipation or loose stools and peripheral vasoconstriction (Raynaud’s) as well as brain fog and cognitive difficulties.

Maybe in Long Covid there has been direct damage by the virus to our nervous system, or maybe it is a result of prolonged neuroinflammation? Hopefully time will tell.

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