Objective: To describe the clinical phenotype and brain [18F] FDG patterns in 52 patients exhibiting freezing of gait and/or gait instability as the main clinical features and to analyze the correlation among brain metabolism, clinical and cognitive profile.

Background: Several neurological disorders with different pathological substrates can display overlapping clinical features with freezing of gait as the main clinical manifestation, such us normal pressure hydrocephalus, PSP, PD, among others.

Method: This is a clinical study of 52 adults (mean age 71 ± 16 years), attended from 2018 to 2022. All complained of freezing of gait and/or instability as the principal symptom. Patients with a diagnosis of PD, MSA, or other neurodegenerative disorders with gait impairment were excluded. The following clinical features were recorded: freezing of gait, falls, parkinsonism, dysphagia, dysarthria, hypophonia, oculomotor abnormalities, levodopa response, and cognitive dysfunction. Brain MRI and [¹⁸F] FDG PET scan were available in all patients. [¹⁸F] dopa PET data were available in 33 patients.

Results: The most common clinical phenotype consisted of falls (98%), parkinsonism (85%), oculomotor abnormalities (50%), freezing of gait (40%), dysphagia (23%), dysarthria (20%), hypophonia (20%). Brain MRI showed signs of hydrocephalus (42%), mesencephalic flattening (27%), cortical atrophy (19%) and normal in 12%.

In [¹⁸F] FDG PET scan, dorsolateral and dorsomedial frontal cortex, parietal, basal ganglia, thalamus and midbrain hypometabolism was the most frequent pattern, compatible with the diagnosis of PSP in 77%. [¹⁸F] dopa-PET scan showed decreased tracer uptake in 65%. Dys-executive mild impairment was the main cognitive profile. Levodopa was administered in 73% of patients, with no improvement in 76% and transient benefit in 24%.

Finally, this correlation allowed us to establish the final diagnosis of possible PSP PGF in 52%; probable PSP RS in 13%; probable PSP P in 13%; possible PSP CBS in 4%; possible PSP SL in 2%; possible PSP F in 2%; normotensive hydrocephalus in 12%, and unknown origin in 2%.

Conclusion: [¹⁸F] FDG PET scan can be considered a valuable tool in the differential diagnosis of patients with freezing of gate as the main clinical feature. Although hydrocephalus should be considered the first diagnosis, in several circumstances a neurodegenerative process like PSP-PGF might be the underlying pathology.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/phenotype-and-brain-18f-fdg-patterns-in-patients-with-freezing-of-gait-as-the-main-clinical-feature/