To date, this is the first report of a HD sonographically detected at the ER. This supports the view that pTCS can be easily implemented in the diagnostic algorithms and differential diagnosis of movement disorders, even in urgency settings .
HD is an autosomal dominant disorder caused by an unstable expansion of the trinucleotide CAG on chromosome 4p16.3, leading to a progressive degeneration of the basal ganglia, particularly of the neostriatum . The diagnosis focuses on typical involuntary movements, although the clinical presentation also includes cognitive decline and psychiatric symptoms (i.e. depression, irritability, anxiety, psychosis, and compulsive behavior) . Psychiatric disturbances often precede the onset of motor symptoms , as in the present case, thus challenging an early diagnosis and treatment. Neuroimaging methods, such as CT and MRI, may detect structural abnormalities, although they often report normal findings, especially in the early stages . Indeed, the MRI of our patient did not detect any abnormality, thus highlighting the diagnostic utility of pTCS that might be more sensitive of MRI in early HD. Nuclear imaging methods, i.e. single photon emission tomography and positron emission tomography, can identify biochemical changes in the basal ganglia and brainstem , but they are expensive and not widely accessible.
Although the frequency of late-onset HD (>59 years) is assumed to be low and the clinical course milder, the previous literature is scarce and often inconclusive. A very recent study on a large cohort  founds that late-onset patients present more frequently with gait and balance problems as first symptoms, and the disease progression is not milder compared to common-onset HD patients, apart from motor progression. Moreover, in this patient subgroup, the family history is likely to be negative, which might make diagnosing HD more difficult, although balance and gait problems are helpful clinical clues . Taken together, these findings are in line with the patient described here; in this context, it is likely that gait and motor disorder had been present for more than two weeks, although neither the patient nor the family members reported them.
The pTCS finding of SN hyperechogenicity indicates a functional impairment of the nigro-striatal dopaminergic system , and is assumed to be based on an increased amount of iron bound to proteins other than ferritin [4,16]. Although SN hyperechogenicity is characteristic for idiopathic Parkinson’s disease (PD), it has been reported also in other conditions, such as atypical parkinsonism, spinocerebellar ataxia, and HD [17–19]. In particular, Postert and colleagues  observed SN hyperechogenicity in 12 out of 45 patients with HD (27%), of the caudate nuclei in 6 (13%), and of the lentiform nuclei in 4 (9%). This condition leads to changes of iron-protein binding, which may cause echogenic alterations similar to the SN hyperechogenicity observed in PD . This is also in agreement with molecular studies indicating the essential role of huntingtin in cellular iron homeostasis .
We also can confirm the pathologic signal of the caudate nuclei in HD, a finding that supports the discrimination from other movement disorders . An association between caudate nuclei hyperechogenicity and increased signal intensity in T2-weighted MRI in HD has been reported . However, the precise morphological interpretation is still speculative and further neuropathological and multimodal imaging studies are needed. Recently, Rosas and coworkers  performed functional MRI and mass spectrometry to demonstrate increased iron levels in the basal ganglia and cortical structures both in presymptomatic gene carriers and HD patients.
Finally, it is worth mentioning that this patient was taking amisulpride, a benzamide blocking or antagonizing the presynaptic dopamine D2 receptor. As such, amisulpride is among the neuroactive compounds able to induce tardive dyskinesia, although the prevalence of amisulpride-induced movement disorder is substantially lower than that of the first-generation antipsychotic agents. Moreover, tardive dyskinesias commonly manifests with oro-facial movements, tremor, dystonia, akathisia, and parkinsonism . Since oro-facial dyskinesia was present also in the present case, a iatrogenic cause needed to be taken into account. However, the execution of pTCS at the ER allowed to detect clear signs of an underlying neurodegenerative process and, concomitantly, to exclude a drug-induced effect (where pTCS is normal).
As known, pTCS has several limitations, including the temporal acoustic bone window (insufficient in 5–10% of caucasian individuals ), the operator expertise, and the quality of the ultrasound system. Therefore, reference values need to be obtained specifically for each TCS system and laboratory .
In conclusion, in clinically suspected cases, pTCS can feasibly extend the neurological examination by providing diagnostic clues more rapidly and less expensively than neuroimaging. Further systematic studies are needed to confirm the clinical diagnostic utility of pTCS in patients with movement disorders presenting at the ER.