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This highlights the importance of

1

H MRS to

prove the presence of hepatic encephalopathy,

even when the blood analyses are normal.

Future studies include the investigation of the

metabolic profile in patients with hepatic

encephalopathy before and after treatment,

either medical or surgical. Another future project

would include the investigation of hepatic

encephalopathy in feline patients. It is suspected

that the pathophysiology in cats with hepatic

encephalopathy may be slightly different from

that found in dogs, since they respond in very

variable ways to medical and surgical treatments.

Shown in Fig. 3 is the typical short echo time

magnetic resonance spectra of a malignant

tumour (glioblastoma multiforme) in a nine-year-

old dog. The high peak of choline, extremely low

N-

acetylaspartate and the high amount of lipids

correlate with a high degree of necrosis.

Neoplastic and inflammatory

brain diseases

Intracranial neoplasias and meningoencephalitis

are common diseases in dogs. Conventional

MRI allows characterising the morphology of the

lesion; however, it is not always possible to

distinguish between a neoplastic process and

an inflammatory one. This is crucial because the

treatment, as well as the prognosis, may be

quite different.

We performed

1

H MRS in the brain of dogs with

neoplasia and inflammatory meningoencephalitis

in order to study the metabolic profile of these

diseases and to investigate if there were any

metabolites that could serve as indicators for

of the brain, including thalamus, parietal lobes, temporal lobes and

occipital lobes (Fig. 1), basal ganglia and cerebellum.

This study showed no differences between right and left hemispheres

and no differences between sexes. Statistically, significant metabolite

concentration in different regions of the brain was found. For instance,

the concentration of

N-

acetylaspartate was highest in the parietal lobes

and lowest in the cerebellum, whilst the choline concentration was

highest in the basal ganglia and lowest in the occipital lobe. This study

provided reference values for clinical and research studies employing

similar

1

H MRS technique. What follows are various clinical applications.

Brain metabolite abnormalities in dogs

Hepatic encephalopathy is a neurological condition associated with failure

of the liver to detoxify neurotoxins. The pathogenesis is complex, but it

appears that ammonia plays a central role in the damage of the brain.

Ammonia is produced primarily in the gastrointestinal tract. Typically, a

high amount of ammonia is extracted by the liver via the urea cycle. When

the liver function is not correct, the ammonia accumulates in the brain,

and, once there, the astrocytes are responsible for ammonia detoxification.

The ammonia gets metabolised and converted into glutamine. Too high

levels of glutamine in the brain produce brain oedema and the neurological

signs characteristic of hepatic encephalopathy.

1

H MRS was performed in the brain of six dogs with hepatic

encephalopathy (because of portosystemic shunts or chronic hepatitis),

and they were compared to 12 normal dogs. We found characteristic

differences between these groups: dogs with hepatic encephalopathy

showed high levels of glutamine and lower levels of myo-inositol (Fig. 2).

Furthermore, choline and

N-

acetylaspartate concentration were slightly

lower in dogs with hepatic encephalopathy than in the control dogs.

In some dogs, the concentration of ammonia in blood was normal.

I S S U E S E V E N

H O R I Z O N 2 0 2 0 P R O J E C T S : P O R TA L

www.horizon2020projects.com

106

M E D I C A L T E C H N O L O G Y & R E S E A R C H

Fig. 2 Single voxel

short echo time

magnetic resonance

spectroscopy on the

basal ganglia region of

a seven-year-old golden

retriever with chronic

liver disease and

hepatic encephalopathy

Fig. 3 Typical short

echo time magnetic

resonance spectra of a

malignant tumour in a

nine-year-old dog