Motor Neurone Disease (MND / ALS)

Amyotrophic lateral sclerosis (ALS) is the most common form of the motor neuron diseases. The disorder is characterized by rapidly progressive weakness, muscle atrophy and fasciculations, muscle spasticity, difficulty speaking (dysarthria), difficulty swallowing (dysphagia), and decline in breathing ability. The disorder causes muscle weakness and atrophy throughout the body caused by degeneration of the upper and lower motor neurons. Unable to function, the muscles weaken and atrophy.

Affected individuals may ultimately lose the ability to initiate and control all voluntary movement, although bladder and bowel sphincters and the muscles responsible for eye movement are usually, but not always, spared. Sensory nerves and the autonomic nervous system are generally unaffected meaning the majority of people with ALS will maintain sight, hearing, touch, smell, and taste. Bladder and bowel functions are also rarely affected by ALS.

The earliest symptoms of ALS are typically obvious weakness and/or muscle atrophy. Other presenting symptoms include muscle fasciculation (twitching), cramping, or stiffness of affected muscles; muscle weakness affecting an arm or a leg; and/or slurred and nasal speech. The parts of the body affected by early symptoms of ALS depend on which motor neurons in the body are damaged first.

About 75% of people contracting the disease experience “limb onset” ALS, i.e., first symptoms in the arms or legs. Patients with the leg onset form may experience awkwardness when walking or running or notice that they are tripping or stumbling, often with a “dropped foot” which drags gently along the ground. Arm-onset patients may experience difficulty with tasks requiring manual dexterity such as buttoning a shirt, writing, or turning a key in a lock.

Occasionally, the symptoms remain confined to one limb for a long period of time or for the whole length of the illness; this is known as monomelic amyotrophy.

About 25% of cases are “bulbar onset” ALS. These patients first notice difficulty speaking clearly or swallowing. Speech may become slurred, nasal in character, or quieter. Other symptoms include difficulty swallowing and loss of tongue mobility.

A smaller proportion of patients experience “respiratory onset” ALS, where the intercostal muscles that support breathing are affected first. A small proportion of patients may also present with what appears to be frontotemporal dementia, but later progresses to include more typical ALS symptoms.

Over time, patients experience increasing difficulty moving, swallowing (dysphagia), and speaking or forming words (dysarthria). Symptoms of upper motor neuron involvement include tight and stiff muscles (spasticity) and exaggerated reflexes (hyperreflexia) including an overactive gag reflex. An abnormal reflex commonly called Babinski’s sign also indicates upper motor neuron damage. Symptoms of lower motor neuron degeneration include muscle weakness and atrophy, muscle cramps, and fleeting twitches of muscles that can be seen under the skin (fasciculations). Around 15–45% of patients experience pseudobulbar affect, also known as “emotional lability”, which consists of uncontrollable laughter, crying or smiling, attributable to degeneration of bulbar upper motor neurons resulting in exaggeration of motor expressions of emotion. To be diagnosed with ALS, patients must have signs and symptoms of both upper and lower motor neuron damage that cannot be attributed to other causes.

Although the order and rate of symptoms varies from person to person, eventually most patients are not able to walk, get out of bed on their own, or use their hands and arms. Regardless of the part of the body first affected by the disease, muscle weakness and atrophy spread to other parts of the body as the disease progresses. In limb-onset ALS, symptoms usually spread from the affected limb to the opposite limb before affecting a new body region, whereas in bulbar-onset ALS symptoms typically spread to the arms before the legs.

Disease progression tends to be slower in patients who are younger than 40 at onset, have disease restricted primarily to one limb, and those with primarily upper motor neuron symptoms. Conversely, progression is faster and prognosis poorer in patients with bulbar-onset disease, respiratory-onset disease, and frontotemporal dementia.

Difficulty swallowing and chewing making eating normally very difficult and increase the risk of choking or aspirating food into the lungs. In later stages of the disease, aspiration pneumonia and maintaining a healthy weight can become a significant problem and may require insertion of a feeding tube. As the diaphragm and intercostal muscles (rib cage) that support breathing weaken, measures of lung function such as forced vital capacity and inspiratory pressure diminish. In respiratory onset ALS, this may occur before significant limb weakness is apparent. External machines such as bilevel positive pressure ventilation (BiPAP) are frequently used to support breathing, first at night, and later during the daytime as well. BiPAP is only a temporary remedy, however, and it is recommended that long before BiPAP stops being effective, patients should decide whether to have a tracheotomy and long term mechanical ventilation. Most people with ALS die of respiratory failure or pneumonia.

Although respiratory support can ease problems with breathing and prolong survival, it does not affect the progression of ALS. Most people with ALS die from respiratory failure, usually within three to five years from the onset of symptoms. The median survival time from onset to death is around 39 months, and only 4% survive longer than 10 years.

PBP is a disease that attacks the nerves supplying the bulbar muscles. These disorders are characterized by the degeneration of motor neurons in the cerebral cortex, spinal cord, brain stem, and pyramidal tracts. This specifically involves the glossopharyngeal nerve (IX), vagus nerve (X), and hypoglossal nerve (XII).

Prognosis for PBP patients is poor. Progressive bulbar palsy symptoms can include progressive difficulty with chewing, talking, and swallowing. Patients can also exhibit reduced gag reflexes, weak palatal movements, fasciculations, and weak movement of the facial muscles and tongue. In advanced cases of PBP, the patient may be unable to protrude their tongue or manipulate food in their mouth.

Patients with early cases of PBP have difficulty with pronunciations, particularly lateral consonants (linguals) and velars, and may show problems with drooling saliva. If the corticobulbar tract is affected a pseudobulbar affect with emotional changes may occur.

Because PBP patients have such difficulty swallowing, food and saliva can be inhaled into the lungs. This can cause gagging and choking, and it increases the risk of pneumonia. Death, which is often from pneumonia, usually occurs 1 to 3 years after the start of the disorder.

Is a rare subtype of motor neuron disease (MND) which affects only the lower motor neurones. PMA is thought to account for around 4% of all MND cases. This is in contrast to amyotrophic lateral sclerosis (ALS), the most common form of MND, which affects both the upper and lower motor neurones, or primary lateral sclerosis, another rare MND variant, which affects only the upper motor neurons. The distinction is important because PMA is associated with a better prognosis than other forms of MND.

As a result of lower motor neurone degeneration, the symptoms of PMA include:

• atrophy
• fasciculations
• muscle weakness

Some patients have symptoms restricted only to the arms or legs (or in some cases just one of either). These cases are referred to as “Flail Arm” (FA) or “Flail Leg” (FL) and are associated with a better prognosis.

Pseudobulbar palsy results from an upper motor neuron lesion to the corticobulbar pathways in the pyramidal tract. Patients have difficulty chewing, swallowing (Dysphagia) and demonstrate slurred speech (Dysarthria) (often initial presentation). Individuals with pseudobulbar palsy also demonstrate inappropriate emotional outbursts.