A term used for diseases of the nuclei of the cranial nerves IX to XII in the medulla.
- Signs are of a lower motor neurone lesion of the tongue and muscles of talking and swallowing. The tongue is flaccid and fasciculating, jaw jerk is absent and speech is quiet, hoarse or nasal.
- Causes – MND, Guillian-Barré, polio, myasthenia gravis, syringobulbia or brainstem tumours.
Aka pseudobulbar palsy - a term used for upper motor neurone lesion of muscles of talking and swallowing due to bilateral lesions above the mid-pons e.g. corticobulbar tracts – affected in multiple sclerosis, motor neurone disease, stroke and central pontine myelinolysis.
- Signs – slow tongue movements with slow speech, increased jaw jerk and pharyngeal reflexes.
MND - definition
A group of major degenerative diseases characterised by loss of neurones in the motor cortex, cranial nerve nuclei and anterior horn cells. Both upper and lower neurones can be affected.
There is no sensory or sphincter disturbance distinguishing it from multiple sclerosis and poly-neuropathies and eye movements are never affected distinguishing it from myasthenia gravis.
MND - epidemiology
The median age of onset is 60 years and the disease is often fatal within 2-4 years.
- Patients – consider MND in patients >40 years with a stumbling spastic gait, foot drop, proximal myopathy and weak grip and shoulder abduction (opening doors and washing hair are difficult).
MND - causes
Unknown but as MND, like polio, affects the anterior horn cells viruses have been suspected.
MND - clinical patterns
Amyotrophic lateral sclerosis – loss of motor neurones in both the motor cortex and anterior horns producing upper motor neurone weakness and lower motor neurone wasting. (50%)
Progressive bulbar palsy – only affects cranial nerves IX to XII but can progress to ALS. (10%)
Progressive muscular atrophy – loss of neurones in the anterior horn cells therefore there are only lower motor lesion signs – distal muscles affected before proximal muscle groups. (10%)
Primary lateral sclerosis – loss of Betz cells in the motor cortex producing upper motor neurone lesion signs – marked spastic leg weakness and pseudobulbar palsy.
MND - diagnosis
No diagnostic test but brain and spine MRI to exclude a structural cause, lumbar puncture to exclude an inflammatory cause and neurophysiology to exclude a motor denervation.
MND - management
A multidisciplinary team approach is essential.
- Anti-glutaminergic drugs – e.g. Riluzole prolongs life by around 3 months and is very costly. Side effects – deranged LFTs, vomiting, weakness, tachycardia, headache and dizziness.
- Treat symptoms – drooling can be treated with amitriptyline 25-50mg TDS, dysphagia can be prevented by blending food or inserting a nasogastric tube, joint pain can be treated with simple analgesia and respiratory failure can be prevented by non-invasive ventilation.
Cervical spondylosis - definition
Spondylosis definition – degenerative osteoarthritis of the joints between spinal vertebrae.
Cervical spondylosis with compression of the cord (myelopathy) and nerve roots is the leading cause of progressive spastic quadriparesis (partial or total loss of all 4 limbs) with sensory loss below the neck.
Cervical spondylosis - most patients
However most people with cervical spondylosis have no impairment – just degeneration of the annulus fibrosis of cervical intravertebral discs ± osteophytes which narrow the spinal canal and intervertebral foramina.
As the neck flexes and extends the spinal cord is damaged as it is dragged over these protruding bony spurs anteriorly and indented by the thickened ligamentum flavum posteriorly.
Cervical spondylosis - signs
Limited, painful neck movement ± crepitus and neck flexion may cause tingling down the spine – a positive Lhermitte’s sign. These findings do not distinguish between cord or root involvement.
Cervical spondylosis - radiculopathy
Nerve root compression – pain in the arms or fingers at the level of the compression, with dull reflexes, dermatomal sensory disturbance (numbness, tingling and decreased pain and temperature sensation), lower motor neurone weakness and eventual wasting of muscles that are innervated by the affected root.
Examine the legs as there may be upper motor neurone signs suggestive of cord compression – spasticity, weakness, brisk reflexes and upgoing plantars.
Cervical spondylosis - differential diagnosis
Multiple sclerosis, nerve root neurofibroma, subacute degeneration of the spinal cord (due to decreased vitamin B12), compression by vertebral or cord tumours.
Cervical spondylosis - investigations
MRI to localise the lesion – an anterior posterior compression ratio >30% usually indicates histopathological changes in the cord. Time to walk 30M can help to monitor progression.
Cervical spondylosis - management
A firm neck collar restricts anterior – posterior movement of the neck and can relieve pain but patients dislike them!
If there is significant MRI abnormalities most patients will benefit greatly from surgical root decompression – a laminectomy (a part of the lamina is removed) or laminoplasty (screws and plates used to lengthen the lamina – associated withless pain and fewer complications).
Myopathy vs neuropathy
In favour of myopathy – gradual onset of symmetrical muscle weakness e.g. difficulty combing hair or climbing stairs, dystrophies usually affect specific muscle groups causing selective weakness on first presentation and preserved tendon reflexes.
In favour of neuropathy – suggested by paraesthesia, bladder problems and distal weakness.
Myopathies - specific symptoms
Excess fatigability – suggests myasthenia.
Rapid onset – neuropathy or a toxic, drug or metabolic induced myopathy.
Pain – at rest and local tenderness suggests inflammatory myopathy or on exercise suggests ischaemia or a metabolic myopathy e.g. McArdle’s disease.
Firm muscles – suggests pseudohypertrophic muscular dystrophy e.g. Duchenne’s.
Lumps – haematoma, herniation of muscle through its fascia or tendon rupture.
Fasciculations – suggests anterior horn cell or nerve root disease.
Myopathies - investigations
Bloods – ESR, CK, AST and LDH may all be raised, electromyography and other tests related to a systemic cause e.g. TFTs, genetic testing and muscle biopsy (should be a last resort).
Muscular dystrophy - definition
A group of genetic diseases with progressive degeneration and weakness of specific muscle groups.
The primary abnormality may be in the muscle membrane. Secondary effects of this are marked variation in size of individual fibres and deposition of fat and connective tissue.
Muscular dystrophy - Duchenne's
The most common dystrophy – X linked recessive disorder affecting 3 in 100,000 male births but 30% occur from spontaneous mutations. The Duchenne gene is on the short arm of the X chromosome and its product – dystrophin is non-functional.
It presents at 4 years of age with increasingly clumsy walking, progressing to difficulty in standing and eventually respiratory failure. Pseudohypertrophy is seen especially in the calf muscles and serum creatinine kinase is >40 times normal.
There is no specific treatment and only some patients survive beyond the age of 20 years but home ventilation improves prognosis.
Muscular dystrophy - Becker's
Affects 0.3 in 1000 male births and results from a Duchenne gene mutation that produces a partially functioning dystrophin. It presents in a similar way to Duchenne muscular dystrophy but is less severe - progression is slower and prognosis better.
Muscular dystrophy - facioscapulohumeral
Aka Landouzy-Dejerine – autosomal dominant inheritance and almost as common as Duchenne’s. It presents at 12-14 years of age with inability to puff out the cheeks and difficulty raising the arms above the head.
Signs – weakness of the face (no expression), shoulders and upper arms, foot drop, winging of the scapula, scoliosis, anterior axillary folds and horizontal clavicles. <20% will need a wheelchair by 40 yrs.
A myotonic disorder is one that causes muscle spasm. It is an autosomal dominant Cl- channelopathy that usually presents at 25 years of age with distal weakness (hand or foot drop), weak sternocleidomastoids and myotonia.
Also causes cataracts, male frontal baldness, diabetes mellitus, testes or ovary atrophy, cardiomyopathy and mental impairment.
Most patients die in middle age due to a concurrent illness. Genetic counselling is very important in these patients.
Inclusion body myositis, polymyositis or dermatomyositis.
Inclusion body myositis – most likely cause if the patient is >50 years old – weakness starts with the quadriceps, finger flexors and pharyngeal muscles. Ventral muscle groups are often more affected than dorsal groups.
Myopathies - drug causes
Alcohol, statins, steroids, chloriquine, zidovudine, vincristine or cocaine.