【Case analysis】Olive pondron cerebellar atrophy

Introduction to the medical history

1.
Male, 66 years old, gradually moving slowly, walking unsteadily, slurred speech for a year, suspected Parkinson's syndrome
.

2.
Female, 65 years old, gradually became numb and weak in her limbs, and walked unsteadily for 4 years
.

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case analysis

The former is clinically diagnosed as cerebellar ataxia.

The latter is clinically diagnosed as hereditary cerebellar ataxia.

Olive pontine cerebellar atrophy HOC (olivopont ocerebellar atrophy)

Olive pontine cerebellar atrophy (OPCA) is a group of degenerative diseases with progressive atrophy of multiple parts of the nervous system of unknown cause, with cerebellar ataxia as the main clinical manifestation.

First reported and named
in 1900 by Dejerine and Thomas.

OPCA can be divided into two types
: hereditary (Menzel type, mostly autosomal dominant inheritance, a few recessive inheritance) and sporadic (Dejrine Thomas type).

The basic pathological feature is neuronal degeneration of the cerebellum, pons and inferior olive nucleus, causing demyelination of cerebellar white matter fibers and fibrogliosis
.

The etiology of non-hereditary OPCA is not fully understood, and the pathogenesis is unknown, and it is speculated that it may be related to
viral infection, free radical damage, biochemical abnormalities, immune factors, etc.

Patients with advanced disease often die
due to complications such as lung infection due to prolonged bed rest.

It tends to occur in adulthood, with an average age of onset of about 30 years old, and there is obvious early onset
.

There are more men than women
.

Insidious onset and progressive exacerbation
.

Slow progressive cerebellar ataxia.

Sometimes it may be accompanied by vertebral and extravertebral symptoms, as well as dementia.

Tachypepic motor disorder is considered a characteristic manifestation
of OPCA.

Imaging tests exclude other organic brain pathologies
.

The main signs of routine head MRI on OPT are:

(1) Brainstem atrophy, morphology thinning, especially the ventral flattening of the pons, anteroposterior diameter reduction is more obvious, this sign is best shown in the MRI sagittal position;

(2) Cerebellar atrophy, hemispheric lobular groove, fissure widening and deepening, "dead dendritic", this sign is better in the MRI axis or sagittal position;

(3) Enlargement of the peribrainstem cistern and four ventricles, of which the widening of the anterior pontoponte pool is the most obvious;

(4) There are generally no abnormal signals in the brain parenchyma, and some patients have mild brain atrophy
.

The cross-shaped hyperintense opacities of the pons can appear on advanced T2WI, known as the "cross sign", which is considered to be decisive for the diagnosis of OPCA
.

The pathological basis may be the degeneration of the pontine nucleus and transverse pontine fibers (fibers emitted by the pontine nucleus that reach the cerebellum through the cerebellar mid-foot), increased water content or iron deposition due to glia-reactive hyperplasia, and the fibrous bundles emitted by the cerebellar dentate nucleus that make up the upper cerebellar foot are not damaged
.

Some domestic scholars have found longitudinal line-like high-signal shadows on T2WI, which is called "longitudinal sign"
.

Horimoto et al.
believe that the "longitudinal sign" is an early manifestation of the "cross sign", that is, the "longitudinal sign" appears first and then the "cross sign"
.

Various imaging changes mostly appear in the middle and late stages of the course of OPCA, and there is a lack of characteristic changes
in the early stage.

The ratio of anterior and posterior diameter of pons to anterior and posterior pool of pontine (B/E), ratio of anterior and posterior diameter of medulla oblongata and anterior pool of medulla oblongata (C/F).

B/E normal is 3.
32～ 5.
28, C/F normal value is 0.
72~2.
68, if the B/E value is less than 3 and the C/F value is less than 1, OPCA should be highly suspected
.

When the anteroposterior diameter of pontine is less than 18mm, the anteroposterior diameter of medulla oblongata is less than 10mm, or the anterior pontine cistern is greater than 12mm, the anterior medullary cistern is greater than 11mm, and the height of the four ventricles is greater than 11.
5mm, PACA can be diagnosed, especially the anterior diameter of the anterior medulla oblongata changes significantly
in OPCA.

differential diagnosis

The clinical manifestations are easily confused with Parkinson's disease, and the misdiagnosis rate has been reported to be as high as about 55%.

Research progress

Recent studies have confirmed that an increase in the local epidiffusion coefficient rADC and anisotropy fraction (FA) values in patients with PACA on DWI indicates myelin involvement
.

Hydrogen proton magnetic resonance spectroscopy studies found that the NAA/Cr peak ratio of the pons was significantly reduced
in PACA patients.