Parkinson's Disease.

N Engl J Med · 2024-06-15 · open original →

Review · N Engl J Med · Tanner CM et al. · cited 180×

Reader summary

by xavier.grehant on 2026-05-14

Disease Mechanisms Genetics Biomarkers and Diagnosis Non-Motor Symptoms Sleep Motor Symptoms Medications Surgical and Device Therapy Emerging Therapies Exercise Cognition and Mood

This 2024 New England Journal of Medicine review by Dr. Caroline Tanner and Dr. Jill Ostrem (University of California, San Francisco) provides a state-of-the-art overview of Parkinson's disease for clinicians. Its central message for patients and families is that Parkinson's is now understood as a whole-body ("multisystem") disorder that begins years—sometimes more than a decade—before the classic tremor or stiffness appears. Symptoms that can precede the motor diagnosis include loss of smell, constipation, acting out dreams during sleep (called REM sleep behavior disorder, or RBD), and mood changes. Recognizing this "prodromal" phase matters because future disease-modifying treatments are most likely to work before large amounts of brain tissue have been lost.

The article explains that genetic testing is increasingly useful: variants in genes such as LRRK2 and GBA1 can predict how a person's disease is likely to progress and may soon guide which experimental therapies they are offered. New lab tests—especially the alpha-synuclein seed amplification assay (αSyn-SAA), which detects abnormal protein in spinal fluid or other samples—are moving Parkinson's diagnosis toward biology rather than symptoms alone, similar to how Alzheimer's diagnosis now uses brain scans and blood tests. A new biological staging system proposed by the Movement Disorder Society is described; it classifies disease from pre-symptomatic biology all the way through advanced stages.

For daily management, the review confirms that levodopa (often combined with carbidopa) remains the cornerstone drug, and that deep brain stimulation (DBS) and focused ultrasound are effective options for suitable patients with medication-resistant tremor or motor fluctuations. Exercise is singled out as beneficial for motor and non-motor symptoms and possibly neuroprotective. The article also surveys an active pipeline of disease-modifying therapies in clinical trials—including drugs targeting LRRK2, GBA1, alpha-synuclein, and the GLP-1 pathway (similar to diabetes drugs like semaglutide)—offering realistic but cautious hope that treatments to slow or stop disease progression may be available within the next decade.

What this article adds

Disease Mechanisms: The article frames Parkinson's as a multisystem alpha-synucleinopathy in which abnormal aggregation of alpha-synuclein protein spreads through the nervous system well before motor symptoms emerge. It underscores that dopamine-neuron loss in the substantia nigra is a late event in a longer biological cascade, reshaping how both diagnosis and future treatment should be timed.
Genetics: The review positions genetic testing as clinically actionable today: LRRK2 variants, GBA1 variants, and rarer mutations such as SNCA duplications each carry distinct prognoses and are now linked to specific drugs in clinical trials. The authors state that detecting these gene variants "may inform prognosis and, potentially, treatment"—a shift from genetics as research curiosity to genetics as a guide for personalized care.
Biomarkers and Diagnosis: The article highlights the alpha-synuclein seed amplification assay (αSyn-SAA) as a major diagnostic advance, able to detect pathological alpha-synuclein in cerebrospinal fluid and other accessible samples with high accuracy even in prodromal individuals. It also describes a new Movement Disorder Society biological staging framework that classifies Parkinson's by underlying biology rather than symptom severity alone, analogous to oncology staging.
Non-Motor Symptoms: The review emphasizes that non-motor features—including loss of smell (hyposmia), constipation, depression, and autonomic dysfunction—are often premonitory, appearing years before diagnosis. Identifying these symptoms early is increasingly important for research and may eventually trigger preventive treatment in at-risk individuals.
Sleep: REM sleep behavior disorder (RBD)—in which people physically act out vivid dreams—is highlighted as one of the strongest prodromal markers of Parkinson's and related synucleinopathies, often preceding motor diagnosis by a decade or more. The article situates RBD within the new biological staging system as evidence of early neurological involvement.
Motor Symptoms: Beyond the classic triad of tremor, rigidity, and bradykinesia, the article details motor complications that develop over time with levodopa therapy—including "wearing-off" (return of symptoms before the next dose) and dyskinesias (involuntary movements). It reviews how device-aided therapies such as continuous intestinal gel infusion of levodopa, DBS, and focused ultrasound are used to manage these fluctuations.
Medications: Levodopa/carbidopa remains the gold-standard symptomatic treatment, and the review provides a current map of adjunct agents—dopamine agonists, MAO-B inhibitors, COMT inhibitors—and how they are sequenced as disease advances. It also introduces the concept that genetic subtype (e.g., LRRK2 vs. GBA1 carrier) may eventually guide initial drug choice as targeted therapies mature.
Surgical and Device Therapy: The article reviews deep brain stimulation (DBS) as the most established surgical option and discusses MRI-guided focused ultrasound (FUS) as a newer, incisionless ablative alternative for appropriate patients—particularly those with tremor-dominant disease or who are not DBS candidates. It covers patient selection criteria and the types of benefit each approach provides.
Emerging Therapies: The review surveys a broad pipeline of disease-modifying trials, including LRRK2 kinase inhibitors, GBA1-targeting agents, anti-alpha-synuclein monoclonal antibodies (such as prasinezumab), antisense oligonucleotides, gene therapies, and GLP-1 receptor agonists (the same class as semaglutide/Ozempic, now in Phase 2/3 trials for Parkinson's). None are yet approved to slow disease progression, but the field is described as more active than at any prior point.
Exercise: The article endorses exercise as a cornerstone of Parkinson's management with evidence for benefits on motor function, balance, and non-motor symptoms, and notes preclinical and early human data suggesting it may have neuroprotective effects. Patients are encouraged to remain physically active at all stages of disease.
Cognition and Mood: Depression, anxiety, apathy, and cognitive decline are described as intrinsic features of the disease rather than purely secondary reactions, arising from neurodegeneration beyond the dopamine system. The review notes these are often undertreated and calls for systematic screening at diagnosis and throughout follow-up.

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