Diagnosis
Differential diagnosis can be challenging due to the number of overlapping symptoms, shared between several motor neuron diseases. Frequently, the diagnosis is based on clinical findings (i.e. LMN vs. UMN signs and symptoms, patterns of weakness), family history of MND, and a variation of tests, many of which are used to rule out disease mimics, which can manifest with identical symptoms. Classification
Motor neuron disease describes a collection of clinical disorders, characterized by progressive muscle weakness and the degeneration of the motor neuron on electrophysiological testing. The term "motor neuron disease" has varying meanings in different countries. Similarly, the literature inconsistently classifies which degenerative motor neuron disorders can be included under the umbrella term "motor neuron disease". The four main types of MND are marked (*) in the table below.All types of MND can be differentiated by two defining characteristics:
Is the disease sporadic or inherited? Is there involvement of the upper motor neurons (UMN), the lower motor neurons (LMN), or both?Sporadic or acquired MNDs occur in patients with no family history of degenerative motor neuron disease. Inherited or genetic MNDs adhere to one of the following inheritance patterns: autosomal dominant, autosomal recessive, or X-linked. Some disorders, like ALS, can occur sporadically (85%) or can have a genetic cause (15%) with the same clinical symptoms and progression of disease.UMNs are motor neurons that project from the cortex down to the brainstem or spinal cord. LMNs originate in the anterior horns of the spinal cord and synapse on peripheral muscles.
Lack of oxygen response may indicate other modalities such as heated humidified high-flow therapy, continuous positive airway pressure or (if severe) endotracheal intubation and mechanical ventilation. .Type 2 respiratory failure often requires non-invasive ventilation (NIV) unless medical therapy can improve the situation. Mechanical ventilation is sometimes indicated immediately or otherwise if NIV fails. Respiratory stimulants such as doxapram are now rarely used.There is tentative evidence that in those with respiratory failure identified before arrival in hospital, continuous positive airway pressure can be helpful when started before conveying to hospital. See also
Ventilation/perfusion ratio
Pulmonary shunt

References
External links
MedlinePlus: Respiratory Failure