Progressive hemiparesis in a 75-year-old man

The clinical spectrum of primary lateral sclerosis

Primary lateral sclerosis is a distinct entity that has recently been classified as a "restricted phenotype" of ALS. It is characterized by a pattern of isolated upper motor neuron involvement that often begins in the legs and spreads diffusely. Distinction from other conditions requires careful consideration of clinical presentation and time course of disease. Mills' Syndrome is a rare unilateral variant of primary lateral sclerosis. Cognitive and behavioral involvement may occur.

Natural History of "Pure" Primary Lateral Sclerosis

OBJECTIVE

To assess whether primary lateral sclerosis (PLS), classified as pure when the EMG is normal, converts to amyotrophic lateral sclerosis (ALS) after longitudinal follow-up.

METHODS

Retrospective chart review was performed of patients with pure PLS at Mayo Clinic in Rochester, MN (1990-2016). Inclusion criteria required a normal EMG during the first 4 years of symptoms.

RESULTS

Forty-three patients had pure PLS (25 female, 58%) with a median onset age of 50 years (range 38-78 years) and median follow-up at 9 years' disease duration (range 4-36 years). The ascending paraparesis phenotype (n = 30, 70%) was most common, followed by hemiparetic onset (n = 9, 21%) and bulbar onset (n = 4, 9%). Among the 30 paraparetic-onset cases, bladder symptoms (n = 18, 60%) and dysarthria (n = 15, 50%) were more common than pseudobulbar affect (n = 9, 30%) and dysphagia (n = 8, 27%). By the last follow-up, 17 of 30 (56%) used a cane and 6 (20%) required a wheelchair. The paraparetic variant, compared with hemiparetic and bulbar onset, had the youngest onset (48 vs 56 vs 60 years, respectively; p = 0.02). Five patients died; 1 patient required a feeding tube; and none required permanent noninvasive ventilation. Two patients developed an idiopathic multisystem neurodegenerative disorder, which surfaced after 19 and 20 years. Two patients developed minor EMG abnormalities. The remainder 39 had persistently normal EMGs.

CONCLUSIONS

Pure PLS did not convert to ALS after a median of 9 years' disease duration follow-up in our study population. The ascending paraparetic phenotype was most common, with earlier onset and frequent bladder involvement. After years of pure PLS, <5% develop a more pervasive neurodegenerative disorder.

Primary lateral sclerosis: diagnosis and management

Primary lateral sclerosis (PLS) is a rare neurodegenerative disorder at the upper motor neurone extreme of the spectrum of motor neurone disease. The diagnosis is clinical and based on the characteristic features of slowly progressive spasticity beginning in the lower limbs, or more rarely with spastic dysarthria, typically presenting around 50 years of age. The absence of lower motor neurone involvement is considered to be a defining feature, but confident distinction of PLS from upper motor neurone-predominant forms of amyotrophic lateral sclerosis may be difficult in the first few years. Corticobulbar involvement in PLS is frequently accompanied by emotionality. While there may be dysphagia, gastrostomy is rarely required to maintain nutrition. Cognitive dysfunction is recognised, though dementia is rarely a prominent management issue. PLS is not necessarily life shortening. Specialised multidisciplinary care is recommended. Increasing international research cooperation is required if the aspiration of dedicated therapeutic trials for PLS is to be achieved.

Mills' syndrome revisited

Mills' syndrome is an idiopathic, slowly progressive, spastic hemiparesis. We describe three cases that have been under review for a minimum of 11 years (range 11-19). In all patients, symptoms started in a leg, with a mean age of onset of 59 years (range 53-63). The only abnormality on laboratory investigations was a mildly elevated CSF protein in one case. MRI demonstrated focal T2 hyper-intensity located eccentrically in the cervical cord ipsilateral to the symptomatic side. No cerebral abnormality was demonstrated. Whilst visual and somatosensory evoked potentials were unremarkable, motor evoked potentials were abnormal in all patients: central motor conduction times were significantly prolonged unilaterally in two patients and bilaterally but asymmetrically in the third. Beta-band (15-30 Hz) intermuscular coherence, a potentially more sensitive method of assessing upper motor neuron integrity, was absent unilaterally in one patient and bilaterally in the other two. One patient developed amyotrophy and thus a picture of amyotrophic lateral sclerosis after 16 years, suggesting that Mills' syndrome is part of the motor neuron disease spectrum. Both amyotrophy and subclinical contralateral upper motor neuron disease can therefore be features of Mills' syndrome. However, even with the most sensitive electrodiagnostic techniques, unilateral upper motor neuron disease can remain the only abnormality for as long as 10 years. We conclude that whilst Mills' syndrome should be classified as a motor neuron disorder, it is a distinct nosological entity which can be distinguished from amyotrophic lateral sclerosis, upper motor neuron-dominant amyotrophic lateral sclerosis and primary lateral sclerosis. We propose diagnostic criteria for Mills' syndrome, and estimate a point prevalence of at least 1.2:1,000,000 based on our well-defined referral population in the North of England.