Overview.
Olivopontocerebellar cerebellar atrophy (OPCA), a chronic degenerative disease of the central nervous system, is characterized pathologically by marked cerebral pontine and cerebellar atrophy, with cerebellar ataxia and brainstem damage as the main clinical manifestations.In 1891, Menzel first reported 2 patients with clinical manifestations of Parkinson’s syndrome, autonomic failure, and pyramidal fasciculus damage, which are consistent with the current multiple system atrophy (MSA) Clinical and pathologic changes. 1900 Dejerine and Thomas named the group of patients presenting with this clinical presentation olivopontocerebellar atrophy. Subsequent neurological and pathological studies have revealed that many patients with olivopontocerebellar atrophy have a familial predisposition to autosomal dominant or recessive inheritance, which is now categorized as SCA-1 type of hereditary spinal cerebellar ataxia (SCA). Some sporadic cases of olivocerebellar pontine cerebellar atrophy are characterized by mild cerebellar ataxia, on the basis of which choking on drinking water and dysphagia gradually appear, and are often combined with obvious symptoms of Parkinson’s syndrome and autonomic failure during the course of the disease. A small number of patients may have one or two or more of the symptoms of bilateral pyramidal signs, limb muscle atrophy, nystagmus, or extraocular muscle paralysis. It is currently believed that only patients with disseminated forms are categorized as having multiple system atrophy.
Etiology
Patients with olivopontocerebellar atrophy have a familial predisposition to autosomal dominant or recessive inheritance, and are now categorized as SCA-1 in hereditary spinocerebellar ataxia. Only patients with the disseminated form are categorized as having multiple system atrophy.
Symptoms
The disease starts in middle age or pre-senile age, the average age of onset is about 50 years old, the ratio of male to female is 1:1, the onset of the disease is insidious, and the progression is slow.
1. Cerebellar ataxia
Cerebellar dysfunction is the most prominent symptom of this disease, which is characterized by progressive cerebellar ataxia. It appears in the early stage and manifests in both lower limbs, often complaining of lower limb weakness, fatigue, easy to fall and seek medical treatment. Slow and inflexible voluntary movement, unsteady gait, balance disorder, basal widening, trunk sway. Gradually, there is an inability to perform fine movements of the two upper limbs, and clumsiness and unsteadiness of movements. Ataxia of the limbs and trunk is progressively aggravated. As a result of cerebellar dysfunction, dizziness, dysarthria (bardic speech), and intentional tremor occur. Involvement of the medullary muscle group appears dysphagia, choking on drinking water, tongue muscle atrophy and tongue muscle fibrillation, etc.; in rare cases, soft palate myoclonus can be seen; there are also some cases of facial muscle fasciculation tremor, and facial nerve paralysis; in a small number of cases, there can be distal limb muscular atrophy and fasciculation tremor.
2. Nystagmus and ocular motility disorders
Nystagmus is more common in patients with this disease, and supranuclear ophthalmoplegia such as difficulty in upgaze can also occur, which can also be manifested as convergence disorder and extraocular muscle dyskinesia. Slow nystagmus, or slowed sweeping movements, may be a characteristic clinical hallmark of olivary pontine cerebellar atrophy, the mechanism of which is unknown. Optic nerve atrophy and optic papilla pallor may be present.
3. Autonomic dysfunction
For example, upright hypotension, flaccid bladder (urinary incontinence or retention), sexual dysfunction and sweating disorders.
4. Signs of the pyramidal tract
In this disease, there is often involvement of the pyramidal tract, with increased muscle tone/hyperreflexia, or a positive extensor plantar reflex/pathognomonic sign. However, clinically, the symptoms of the pyramidal tract are mild.
5. Extrapyramidal system
Some patients develop signs and symptoms of extrapyramidal disorders in the late stage, such as cogwheel-like ankylosis of the limbs, mask face, and resting tremor. In the middle and late stages of the disease, some patients show different degrees of dementia, characterized by subcortical dementia, the mechanism of which is not yet clear.
Examination
1. Normal cerebrospinal fluid
Cerebrospinal fluid acetylcholinesterase has been reported to be decreased in some cases.
2. Blood biochemical examination
Measurement of plasma norepinephrine and 24-hour urine catecholamine levels may be significantly reduced.
3. Cranial CT examination
Cerebellar and brainstem atrophy. However, negative CT does not exclude the diagnosis of this disease.
4. Cranial magnetic resonance examination
It shows atrophy of the brainstem and cerebellum, and the atrophy of the cerebellar pons is clearly visible. Some studies have pointed out that in addition to cerebellar and brainstem atrophy, olivopontine cerebellar atrophy is often accompanied by reduced nigrostriatal signals, but rarely by reduced signals of the nucleus accumbens, according to which, olivopontine cerebellar atrophy can be differentiated from SDS and SND, which are often accompanied by reduced signals of the nucleus accumbens, especially the posterior-lateral portion of the nucleus accumbens. Magnetic resonance can clearly show the anatomical structure of the posterior cranial fossa, which is considered to be the best neuroimaging method for the diagnosis of olivopontocerebellar atrophy.
5. Brainstem auditory evoked potentials
It shows prolonged latency of wave I, II and III.
6. Nystagmus electrogram
(1) Horizontal gaze nystagmus is present.
(2) Decreased slow-phase velocity of optokinetic nystagmus.
(3) A step-like curve in the eye-tracking test.
(4) Failure of visual suppression by cold temperature test.
Diagnosis
Diagnosis of this disease currently lacks specific laboratory diagnostic methods, and relies mainly on clinical manifestations, CT and magnetic resonance scans that show varying degrees of cerebellar and brainstem atrophy, and the exclusion of other diseases. Diagnostic points:
1. onset in late middle age, sporadic.
2. Chronic progressive cerebellar ataxia was the prominent clinical manifestation.
3. In addition to cerebellar symptoms, there are multi-system involvement manifestations, such as brainstem involvement manifested as supranuclear oculomotor dyskinesia, slow eye movement; can also involve the extrapyramidal system, the pyramidal system and the autonomic nervous system.
4. Progressive mental decline may be manifested.
5. CT or MRI shows brainstem/brain atrophy.
Treatment
There is no specific treatment for the disease and it is usually treated with supportive and symptomatic therapy. Pregnancy can exacerbate the condition, so avoidance of pregnancy is recommended.