Global Health Asia-Pacific September 2020 September 2020 | Page 48
Feature
How COVID-19 affects
the nervous system
Dr Prem Pillay discusses the effect of the coronavirus pandemic in the first instalment in a series on clinical advances in
neurosciences in 2020
The earliest
indications of
the nervous
system effects
came from the
growing number
of reports that
patients with
COVID-19 were
presenting with
anosmia (loss
of smell) and
ageusia (loss of
taste)
The world of 2020 has completely changed
because of the COVID-19 pandemic. In this
review of the latest advances in neurosciences,
the effects of COVID-19 on the nervous system are the
main topic of the first part of our series.
In the initial phases of the COVID-19 pandemic,
most of the medical fraternity was focused on the
�u-like and respiratory effects of the coronavirus
infection. Establishing an early diagnosis based on
these symptoms, together with PCR based testing,
contact tracing, quarantining of suspected cases,
triaging into hospitals and then into ICU care for
diagnosed cases, was and still is the priority. It’s
only from April 2020 that increased awareness of
the variable clinical manifestations of COVID-19
has become better known. These include not
only respiratory but also cardiac, vascular, renal,
gastrointestinal, haematological, ophthalmological,
and nervous system effects.
The earliest indications of the nervous system
effects came from the growing number of reports that
patients with COVID-19 were presenting with anosmia
(loss of smell) and ageusia (loss of taste). Early studies
suggested that 30 percent of COVID patients self
reported a loss of smell and taste in the early stages of
their disease, including some who were otherwise free
of fever and �u symptoms.
�ater reports, including those that used specific
sensitive tests of smell indicated that up to 98 percent
of patients had a deficit. Anosmia is a better predictor
of COVID-19 than other well-known symptoms, such
as fever and cough. Although it was postulated that
the SARS-CoV-2 virus infected the olfactory nerve
cells directly through the upper nasal cavity, recent
research has shown that these cells do not express
the gene that encodes the ACE2 receptor protein
which this virus uses to enter human cells. It is the
supporting cells of these olfactory neurons that
express this gene that are attacked. This causes
dysfunction but not destruction of the olfactory
neurons leading to anosmia and a secondary loss of
taste. This is one of the reasons that this anosmia and
associated ageusia are usually not permanent and
can recover in most patients over a period of several
weeks.
Although anosmia and ageusia are the more
common manifestations of COVID-19 and are
useful as clinical indicators of an infection, the more
serious side effects of COVID-19 on the nervous
system include strokes and seizures. There have
been increasing numbers of reports of strokes in
COVID-19 patients, including in young patients, and
often in the recovery phase of the disease. Younger
patients, including those in the 30 to 50 year-old age
group, have presented with initially mild symptoms
of COVID-19 followed by a sudden and often
devastating stroke. �ot all of these patients have had
co-morbidities such as hypertension, diabetes, and
Swab test
46 SEPTEMBER-OCTOBER 2020 GlobalHealthAndTravel.com