Mechanisms of development
The functioning of the motor system directly depends on the balance within the basal ganglia. Pathology leads to:
- Activation of the indirect pathway, which enhances inhibitory influences.
- Increased activity of the subthalamic nucleus.
- Inhibition of glutamatergic neurons in the thalamus.
The final result is "network inhibition", which decreases the activity of the motor areas of the cortex, clinically manifesting as akinesia or rigidity.
Clinical Forms
Movement disorders are classified by symptom predominance:
| Type | Main features |
|---|---|
| Akinetic-rigid | Hypokinesia, absence of synkinesias, "frozen shoulders" |
| Tremor | Low-frequency resting tremor (4–6 Hz) |
| Mixed | Uniform combination of akinesia, rigidity, and tremor |
Symptomatic parkinsonism
It is important to distinguish the idiopathic form from the symptomatic form caused by external factors:
- Drug-induced: use of neuroleptics, antiemetics, or calcium channel blockers.
- Organic: consequences of encephalitis, ischemia, or intoxications.
- Plus-parkinsonism syndrome: combination with damage to other CNS structures (e.g., in multiple system atrophy or progressive supranuclear palsy).
Briefly: answers to topical questions
Which diseases belong to the plus-parkinsonism syndrome?
The plus-parkinsonism syndrome (atypical parkinsonism) includes the following multisystem neurodegenerative diseases:
- Progressive supranuclear palsy — Steele-Richardson-Olszewski syndrome.
- Multiple system atrophy — characterized by pronounced autonomic disorders and cerebellar involvement.
- Corticobasal degeneration — manifests with myoclonus, dystonia, and alien hand syndrome.
- Dementia with Lewy bodies — accompanied by early cognitive impairment and visual hallucinations.
Mutations in which genes lead to the development of Parkinson's disease?
Monogenic forms of Parkinson's disease are associated with mutations in the following genes:
- Gene encoding $\alpha$-synuclein — loci PARK 1 and PARK 4 (autosomal dominant inheritance).
- Parkin gene — locus PARK 2 (autosomal recessive inheritance).
- PINK-1 gene — locus PARK 6 (autosomal recessive inheritance).
- DJ-1 gene — locus PARK 7 (autosomal recessive inheritance).
- LRRK2 gene — locus PARK 8 (autosomal dominant inheritance).
- ATP13A2 gene — locus PARK 9 (autosomal recessive inheritance).
- FBXO7 gene — locus PARK 15 (autosomal recessive inheritance).
Variants of the GBA gene are associated with a moderate risk of developing Parkinson's disease.
How is dystonia classified according to localization and distribution in the body?
According to the localization and distribution of the pathological process, dystonia is classified into the following forms:
- Focal — observed only in one part of the body (e.g., blepharospasm or spasmodic torticollis).
- Segmental — involves two adjacent body regions.
- Multifocal — manifests in several different parts of the body.
- Hemidystonia — affects the limbs, trunk, and face on one side only.
- Generalized — spreads to various muscles of the trunk, face, and limbs.
What forms of dystonia exist according to etiology?
According to etiology, dystonia is divided into two forms:
- Primary dystonia — diagnosed based on the clinical picture, exclusion of diseases causing secondary dystonia, and detection of genetic mutations in some patients.
- Secondary (symptomatic) dystonia — associated with other pathological conditions; its causes are similar to those of secondary parkinsonism.
"HAR" — Hypokinesia, Akinesia (rigidity), Rhythmic tremor. This is a triad that helps remember the main manifestations of movement disorders.
Class and exam questions
What is the difference between the idiopathic form and symptomatic parkinsonism?
The idiopathic form is a primary neurodegenerative disease. Symptomatic forms are caused by external causes: medication intake, infections, or vascular lesions.
What is "lead-pipe rigidity"?
This is a constant increase in muscle tone characteristic of parkinsonism, in which the limb retains the position given to it.
Why is movement impaired in Parkinson's disease?
Due to the cessation of dopaminergic impulses to the striatum, which disrupts the basal ganglia loop connections and suppresses motor cortex activity.
What else to study on this topic
- The role of the $\alpha$-synuclein protein and Lewy bodies in neurodegeneration.
- Genetic loci (PARK1–PARK16) and inheritance types.
- The clinical triad of Steele-Richardson-Olszewski syndrome.
- The pathogenetic cascade in Huntington's disease.
- The impact of gene polymorphisms (MAPT, HLA, GAK) on the risk of developing the disease.
Master the entire topic in the "Neurology" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Dystonia" and 907 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 32 video lessons for the subject
Other topics in the section "DeMyer's The Neurologic Examination" / "Duus' Topical Diagnosis in Neurology"
Entire section "Topical Diagnosis in Neurology"Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.