Though criteria for diagnosing amyotrophic lateral sclerosis (ALS) were repeatedly modified and adapted according to the needs of clinicians, diagnosing ALS is still challenging [1-3]. This is because diagnosing ALS relies on progressive abnormalities on clinical and electrophysiological investigations and the absence of differentials that could explain the clinical presentation. There is no single biomarker or other laboratory parameter, which would allow a quick and reliable diagnosis even in the early stages of the disease. The diagnosis is even more challenging if neurological and non-neurological abnormalities are present, which are usually not associated with ALS and do not fit to the definition of ALS, as in the following case.

A 72yo non-smoking Caucasian male, height 170cm, weight 79kg, was admitted for dyspnea with respiratory acidosis. He had a 7y-history of diabetes and a 2y history of progressive gait disturbance with recurrent falls complicated by rib fractures 1y ago, a subdural hematoma 6m earlier, and a right-sided shoulder trauma. Until 2m before admission he was able to walk with a walker and was using a wheel chair since then. He had had a massive alcohol problem until 3y earlier. Additionally, the history was positive for transient bilateral amaurosis 2y earlier. Diagnostic work-up following a syncope after application of nitroglycerine 18m ago, revealed arterial hypertension, atrial fibrillation, bradycardia as low as 40beats/min, myocardial thickening, mitral insufficiency, hyperlipidemia, hyperuricemia, hepatopathy, and hyper-CK-emia up to 409U/l (n, <171U/l). Cerebral CT and MRI showed a right-sided thalamic lacuna, leucaraiosis, and non-specific areal white matter lesions. He scored 24 of 30 points on the mini-mental state examination. Oral anticoagulation was waived because of the falls. Since then he developed cold feet and paresthesias of the distal lower limbs. The family history was positive for diabetes (daughter, sister) and dementia (brother).

Diagnostic work-up for heart failure 12m prior to admission revealed leg edema, persistent atrial fibrillation, pulmonary hypertension, slight mitral and aortic valve insufficiency, enlargement of both atria, small pericardial effusion, and folic acid deficiency. Nerve conduction studies revealed axonal polyneuropathy and cerebral CT showed bilateral basal ganglia and right thalamic lacunas and white matter lesions. Lung disease and peripheral arteriopathy were excluded. Neurological investigations 4m prior to admission revealed progression of weakness and wasting, microangiopathy on cerebral CT, but absence of upper motor-neuron signs, bulbar signs, GM1 or GQ1b antibodies, and CSF, videocinematography, and pulmonary abnormalities. Nerve conduction studies revealed severe axonal degeneration. Needle electromyography revealed fibrillations, fasciculations, denervation, re-innervation but no giant potentials in three muscles. The Schallong-test was slightly abnormal. Despite these non-typical findings the patient was diagnosed as having ALS and riluzole was begun.

On admission the patient was awake and talkative but compromised by dyspnoe. Except for proBNP elevated to 1759pg/nl (n, <278pg/nl) all other serum parameters including HbA1c, renal and liver function parameters, electrolytes, folic acid, vitamin B12, creatine-kinase, and serum lipids were normal. Blood gas analysis showed respiratory acidosis with a maximal pCO2 value of 78mmHg. ECG showed atrial fibrillation. Transthoracic echocardiography revealed normal systolic function, enlarged atria, restrictive filling pattern, and myocardial thickening. Clinical neurologic examination one day after admission revealed left-sided hypoacusis (previous tympanic rupture), temporal disorientation, diffuse weakness of the left arm and distal weakness of the right arm (M4+ to M4-), bilateral weakness with distal predominance of the lower limbs (M4+ to M3-), reduced biceps, triceps and patella tendon reflexes with left-sided predominance, absent Achilles tendon reflexes, fasciculations of the intrinsic hand muscles, stocking-type hypaesthesia and dysaesthesia bilaterally, and gynecomastia. There were neither bulbar nor pyramidal signs. On the third hospital day the patient awaked at night with lung edema but recovered under nitroglycerin, diuretics and morphium. On the next morning he could not be contacted anymore and had severe dyspnea again. A neurologist from outside the hospital recommended “comfort care” why cardiac treatment was discontinued without further examinations and morphium subcutaneously was begun. The patient died a few hours later.

According to the revised El Escorial [2], the Airlie-House criteria,[3] and the Awaji-shima criteria [1], the diagnosis of ALS requires the presence of upper and lower motor-neuron affection, progression of these abnormalities on clinical, electrophysiologic, or neuropathologic examination and absence of neuroimaging, electrophysiologic, or pathologic evidence of other disease processes that might explain upper or lower motor-neuron degeneration (Table 1). The presented patient, initially diagnosed as axonal polyneuropathy, did not fulfill the Awaji-shima criteria because of absent upper motor-neuron signs, stocking-type sensory disturbances, and causes other than ALS that could explain respiratory insufficiency. Though he did not fulfill the Awaji-shima criteria and though treating physicians themselves expressed some doubt about their diagnosis, he was misdiagnosed as ALS on his second neurological presentation and thus received an etiquette, which strongly influenced his outcome.

Arguments for axonal sensorimotor polyneuropathy in the presented patient are the history (long-term alcohol abuse, diabetes, folate deficiency), the clinical examination (quadruparesis with distal predominance), reduced/absent tendon reflexes, fasciculations, stocking-type sensory disturbances), and the instrumental findings (axonal lesion on nerve conduction studies, neurogenic electromyography). It cannot be definitively excluded, however, that polyneuropathy had a hereditary component since he was abstinent from alcohol since 3y, and since folate levels and diabetes were well-controlled on his final admission. At least diabetes and cognitive impairment could be hereditary but it cannot be excluded that the patient suffered from a genetic multisystem disorder. It also cannot be excluded that there was a muscle disease (recurrent CK- elevation), which predominantly affected the respiratory muscles and remained undetected due to the dominance of polyneuropathy. Since fasciculations are not unique to ALS, they neither exclude polyneuropathy nor myopathy [4-6].

Dyspnea in the presented patient can be attributed to heart failure or undetected myopathy. Possible causes of heart failure were restricted cardiomyopathy, atrial fibrillation, pulmonary hypertension, pulmonary embolism, heart valve abnormalities, or arterial hypertension. Coronary artery disease, which has not been excluded by coronary angiography in this patient, could be another explanation [7] but was rather unlikely given the well-controlled diabetes, hyperlipidemia, and blood pressure. Additionally, MR-angiography of the cerebral vessels did not show significant atherosclerosis and carotid ultrasound and ultrasound of the lower limb arteries were normal. A further argument for dyspnea due to heart failure is the beneficial effect of antidiuretic treatment in the night before decease. Hypercapnia with normal oxygen saturation not only reflects muscular respiratory insufficiency but may also occur with heart failure itself [8]. Particularly, high output heart failure, which is a feature of restrictive cardiomyopathy [9], may go along with hypercapnia [10]. Additionally, hypercapnia may be explained with pulmonary hypertension [11].

This case shows that ALS should be diagnosed only if the Awaji-shima criteria are fulfilled and if all differentials were profoundly excluded. Respiratory insufficiency should not be attributed to bulbar involvement in ALS as long as cardiac, pulmonary, or myopathic causes were excluded.

The authors confirm that this article content has no conflicts of interest.