Neurological Flashcards
What are the main clinical differences between cerebellar and sensory ataxia?
Sensory ataxia:
- Presence of pseudoathetosis
- Imapired sensation (esepcailly proprioception)
- Past-pointing when eyes closed but not open
Cerebellar ataxia:
- Nystagmus
- Dysarthria
- Past-pointing both when eyes closed and open
What are the common causes of cerebellar ataxia?
Acquired:
- Stroke
- Tumours
- MS
- Trauma
- Intracranial haemorrhage
Metabolic:
- Alcohol
- Toxins
- Thiamine deficiency
- Hypothyroidism
Inherited:
- Spinocerebellar ataxia
- Fiedreich’s ataxia
What are the differentials for isolated bilateral motor neuropathy?
- Motor neuron disease
- Spinal muscular atrophy
- Kennedy’s disease
- Multifocal motor neuropathy with conduction block
What is spinal muscular atrophy?
Spinal muscular atrophy (SMA) is a rare genetic disorder that primarily affects the motor neurons in the spinal cord and brainstem. These motor neurons are essential for controlling voluntary muscle movement. SMA is caused by mutations in the SMN1 gene, which leads to insufficient production of the survival motor neuron (SMN) protein. This protein is crucial for maintaining healthy motor neurons, and its deficiency results in the progressive loss of these neurons, leading to muscle weakness and atrophy.
SMA can vary widely in severity and onset. It is classified into several types, ranging from Type 0, the most severe form, which manifests before birth, to Type 4, a milder form that develops in adulthood. Symptoms often include difficulty with movement, respiratory problems, and delayed motor development. In severe cases, the condition can impact swallowing and breathing.
Diagnosis typically involves genetic testing to confirm the SMN1 mutation. While there is no cure for SMA, advances in treatment, such as gene therapy and SMN2-targeting drugs, have significantly improved outcomes.
Supportive care, including physical therapy and respiratory support, plays a critical role in managing the condition. Early diagnosis and intervention are key to enhancing the quality of life for individuals with SMA.
What is Kennedy’s disease?
Kennedy’s disease, also known as spinal and bulbar muscular atrophy (SBMA), is a rare genetic disorder that primarily affects males. It is an X-linked recessive disease caused by a mutation in the androgen receptor (AR) gene on the X chromosome. This mutation leads to an abnormal expansion of CAG nucleotide repeats, resulting in the production of a defective androgen receptor protein. The disease is characterized by progressive degeneration of motor neurons in the spinal cord and brainstem, leading to muscle weakness and atrophy.
Symptoms of Kennedy’s disease typically begin to manifest in adulthood, often between the ages of 30 and 50. Common symptoms include difficulty with swallowing (dysphagia), muscle cramps, hand tremors, weakness in the limbs, and gynecomastia (enlarged breast tissue in males). As the disease progresses, individuals may experience difficulties with speech, mobility, and breathing, although it typically does not affect life expectancy.
There is currently no cure for Kennedy’s disease, but treatment focuses on managing symptoms and improving quality of life. Physical therapy, occupational therapy, and assistive devices can help maintain mobility and independence. Genetic counseling is recommended for affected individuals and their families to understand the inheritance pattern and potential implications for future generations.
Which sign is pathognomonic for Kennedy’s disease?
Perioral fasciculations
What is multifocal motor neuropathy with conduction block?
Multifocal motor neuropathy with conduction block (MMNCB) is a rare, immune-mediated disorder that affects the peripheral motor nerves. It is characterized by progressive, asymmetric muscle weakness, primarily in the arms and legs, without significant sensory involvement. The condition is caused by conduction blocks in the motor nerves, which disrupt the transmission of electrical signals, leading to muscle weakness and atrophy. MMNCB is often associated with the presence of anti-GM1 antibodies, although their exact role in the disease remains unclear.
Symptoms typically include weakness in the hands and lower arms, cramping, involuntary muscle contractions (fasciculations), and muscle wasting. Wrist drop or foot drop may occur, and the symptoms are often asymmetrical, affecting one side of the body more than the other. Diagnosis involves nerve conduction studies and electromyography to identify conduction blocks and rule out other conditions.
Treatment primarily focuses on immunomodulatory therapies, with intravenous immunoglobulin (IVIG) being the most effective option. IVIG often provides rapid improvement in muscle strength, but maintenance infusions are required for sustained benefits. Other treatments, such as cyclophosphamide, may be considered in severe cases. Early diagnosis and intervention are crucial to prevent further nerve damage and improve the quality of life for individuals with MMNCB.
What are the causes of peripheral neuropathy?
Metabolic:
- Diabetes mellitus
- Hypothyroidism
- Vitamin B1, B16, B12, folate deficiency
Toxic:
- Alcohol
- Heavy metals (lead, mercury, arsenic)
- Drugs (chemotherapy, antibiotics)
Autoimmune:
- Vasculitides
- RA, SLE, Sjogren’s
- CIDP
- Guillain-Barre
Infection:
- Lyme disease
- HIV
Genetic:
- Charcot-Marie-Tooth
How can common metabolic peripheral neuropathies be distinguished from rarer immune-mediated causes?
- Metabolic peripheral neuropathies (e.g. diabetes, alcohol) are generally length-dependent and signs generally start distally, while in immune-mediated neuropathies (e.g. GBS, CIDP) there may be a mix of proximal and distal signs
- Metabolic neuropathies tend to be symmetrical compared with asymmetrical nature of immune-mediated causes
- Metabolic neuropathies generally do not cause prominent sensory ataxia, unlike immune-mediated causes
What are the causes of spastic paraparesis?
Acute:
- Compressive (e.g. prolapsed disc, spinal abscess, spinal tumour)
- Spinal stroke
- Trauma
Subacute:
- Inflammatory (e.g. MS)
- Infective (e.g. VZV, HIV, HTLV1)
- Metabolic (e.g. vitamin B12 deficiency)
Chronic:
- Neurodegenerative diseases (e.g. primary lateral sclerosis)
- Hereditary (e.g. hereditary spastic paraparesis, Friedreich’s ataxia)
What is hereditary spastic paraparesis?
Hereditary spastic paraplegia (HSP) is a group of genetic disorders that cause progressive stiffness and weakness in the lower limbs due to degeneration of the long motor neurons in the spinal cord. It is inherited in various patterns, including autosomal dominant, autosomal recessive, and X-linked forms.
Key Features
- Gradual muscle stiffness (spasticity) in the legs.
- Weakness leading to difficulty walking.
- Urinary urgency in some cases.
- Foot deformities and balance issues.
- Complicated forms may involve neuropathy, ataxia, vision loss, or cognitive impairment.
