An accurate diagnosis of stroke is essential. A detailed clinical history and competent examination are the key to identify which patients have had a stroke and then arranging and interpreting neuroimaging. Symptoms of stroke are typically acute in onset, but they are highly variable depending upon the vascular territory affected. The commonest stroke symptom is limb weakness. 

There are several clinical conditions that could mimic a stroke. Common mimics are seizure, syncope, migraine, space occupying lesion and delirium secondary to sepsis. Brain imaging is useful to exclude stroke mimics and is essential to differentiate ischaemic from hemorrhagic stroke. Stroke recognition instruments such as the ROSIER (Rule Out Stroke In the Emergency Room) scale are useful in the emergency department to aid in recognition of acute stroke. It scores using questions such as has there been loss of consciousness or syncope and has there been seizure activity? Below is an example of a case of an uncommon neurological condition presenting as stroke.

Case vignette
A 55-year-old right-handed female was admitted with sudden onset of generalised headache associated with numbness and weakness in her left leg. She had previously had a cerebral aneurysmal bleed with surgical clipping in 1982. She suffered a subdural haematoma and was treated conservatively in 2008, which had left her with residual left mild hemiparesis. She lives with her husband in their home and uses a walking stick. 

On examination she was fully conscious with a Glasgow coma score (GCS) of 15/15, there was no papilloedema, she was apyrexial, her blood pressure was 140/80mmHg and her heart rate was 84/mt in sinus rhythm. She had dysarthria, grade 4/5 motor weakness in her left upper and lower limbs with spasticity, bilateral extensor planter response, minimal sensory deficit to touch in her left leg and foot, no meningeal signs and no cardiac murmurs were heard. 

Initial clinical impression was recurrent aneurysmal cerebral bleed. Her CT brain did not reveal any significant change and a lumbar puncture test showed normal cell count, no xanthochromia or no oligoclonal bands. Neurosurgical opinion was taken and she was planned for cerebral vascular imaging. Reassessment of clinical examination (extensor bilateral planter response and marked disproportionate wasting of small hand muscles on both sides) together with normal investigations suggested the possibility of alternative neurological diagnosis.

Discussion
The patient presented with relatively acute onset of focal neurological symptoms associated with past history of stroke and subarachnoid haemorrhage. Clinical signs of upper motor neuron lesion (UMNL) were noted such as muscle weakness, wasting, spasticity and speech difficulty. Brain imaging did not confirm stroke neither did it exclude an alternative diagnosis. The initial clinical impression was recurrent stroke or subarachnoid haemorrhage. Consideration for alternative diagnosis was done in view of neurological examination findings of bilateral extensor plantar response and marked small muscle wasting of hands. 

Although no muscle fasciculation was observed, there was a clinical suspicion for motor neurone disease (MND) or cervical myelopathy. A electromyography test result showed widespread denervation in all four limb muscles with abnormal spontaneous fibrillations and fasciculations in many muscles supportive of the diagnosis of MND.

Motor neurone disease
MND is a disease of middle to late life with mean age of onset of 58 years.1 It is a rare condition with an incidence of approximately two in 100,000.2 It is a progressive neurodegenerative disorder of unknown aetiology. Death usually occurs within five years. 

Confirming the diagnosis of MND may be difficult initially until full clinical features are manifest as it is usually insidious in onset and a slowly progressive condition.
MND usually presents as muscle weakness and atrophy. Less common presenting features are fasciculation, gait disorder, dysarthria or respiratory difficulty. It has been suggested that there is a long preclinical period of relative tolerance and compensation before presentation with apparently focal neurological features.3 This prolonged subclinical phase and variable focal neurological presentation poses difficulties in diagnosis in the early stages.

In MND there is degeneration of upper and lower motor neurons leading to a variable combination of upper and lower motor neuron signs. The resulting clinical features vary in their distribution and severity. Striking asymmetry and selective involvement of individual groups of muscles especially hands and forearm and foot and lower leg are characteristic features. This is due to selective involvement of motor neurons in anterior horns of cord both early and late in the disease. 

Weakness and wasting of muscles that are characteristic of lower motor neuron lesion (LMNL) are seen but the selective muscle involvement is variable from case to case. The corticospinal pathways in the spinal cord are similarly asymmetrically affected as some motor neurons show selective resistance to disease. Spasticity and exaggerated reflexes seen are due to upper motor neuron lesion (UMNL). 

The clinical features of MND thereby are the result of interaction of denervation from loss of functional motor neurons, reinnervation by collateral sprouting from neighbouring motor neurons and supranuclear effects from damage to UMN pathway. The abrupt loss of previously well compensated large motor units may produce disproportionate weakness and a clinical picture of rapid deterioration thereby mimicking features of stroke.

Clinical presentations of MND
The three different presentations of MND are based upon relative involvement of upper and lower motor neurons.

Mixed UMN and LMN syndrome
Amyotrophic lateral sclerosis (ALS) is the most typical form accounting for 85% of cases of MND and has both spinal and cortical involvement. The combination of asymmetric weakness and wasting in limbs (LMN sign) is associated with increased tone, brisk reflexes, extensor planter response (UMN sign). Diffuse fasciculations are a typical feature but may be absent initially as in our case.

Pure LMN syndrome
This is progressive muscular atrophy and 10% of cases present without UMN involvement.

Pure UMN syndrome
This is primary lateral sclerosis. These patients do not develop any LMN signs or develop very late in the illness. Features of pseudobulbar palsy (brisk jaw jerk, stiff slow tongue, characteristic spastic dysarthria and emotional lability) may develop with similar features seen in cerebrovascular disease.

Investigation
In typical MND, motor nerve conduction velocity is normal, sensory studies are normal and EMG reveals diffuse fibrillation and fasciculations.

Differential diagnosis and misdiagnosis
In the Scottish MND Register, out of 552 cases registered from January 1989 to December 1992, 53 patients had a revised alternative diagnosis out of which five patients had cerebrovascular disease.4 A similar study of Irish ALS Registry reported a misdiagnosis rate of 7.3%.5 A study of 260 confirmed ALS patients showed that 13% had undergone inappropriate surgery during the previous five years.Fasciculation was noted in 62% of patients at some stage of disease in a retrospective case study of 560 cases of MND done in three teaching centres in London and Oxford.7


Diagnostic criteria for MND
The El Escorial diagnostic criteria are the most commonly used in clinical studies and therapeutic trials in patients with ALS. The revised El Escorial diagnostic criteria have been established through consensus of experts.8 Their purpose was to standardise diagnosis of patients enrolled in clinical trials. As these are stringent criteria by intent, they are likely to include those patients who have fairly advanced disease at the time of ALS/MND diagnosis. 

Conclusion
Several clinical features of MND could mimic stroke such as spasticity, muscle weakness, wasting, dysarthria especially if onset of symptoms is rapid or focal. A detailed neurological examination eliciting and interpreting clinical signs is essential for correct plan of investigations. As MND is heterogenous in presentation, several clinical variants are described with mixture of UMN and LMN signs. 

The revised EL Escorial diagnostic criteria for MND are insufficient to diagnose early disease. This case illustrates pitfalls in diagnosis on a background of a clinical condition present. Stroke is a common neurological condition seen in clinical practice. The challenge was the uncommon neurological condition presenting as stroke.

Conflict of interest: none declared

References

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