Although the pathophysiology of PS is poorly understood, the implication of monoamines has been widely suggested [
13,
15]. According to many Authors, the occurrence of truncal dystonia during several pharmacologic treatments and neurodegenerative disorders (such as Alzheimer disease and parkinsonian syndromes) supported the hypothesis that a complex dysregulation of multiple neurotransmitter systems are involved [
13,
16]. Both an excess of cholinergic transmission and a decrease of dopaminergic tone could be implied in some cases because of causative effect of cholinesterase inhibitors and/or antagonist effects of neuroleptics on type-2 dopamine (D2) and type-2 serotonin (5HydroxyTriptamine, 5HT-2) receptors [
15]. Down-regulation of postsynaptic norepinephrine (NE) and 5HT-2 receptors induced by antidepressant drugs may also determine a dysfunction of brain stem pathways involved in axial tone control [
17]. In parkinsonian syndromes, PS and other lateral truncal dystonia has been related not only to pharmacological treatment, but also to the clinical stage of the disease [
18]. An imbalance in the dopaminergic-cholinergic system, depending both on the progression of nigrostriatal pathology and on pharmacological treatment has been postulated in PD [
18,
19]. Supporting the neurotransmitters hypothesis, efficacy of anticholinergic drugs and switching therapy to less cholinergic antipsychotics, such as quetiapine or clozapine has been described in some reports [
15]. To our knowledgement, this is the first case of secondary PS not related to both pharmacological intervention and neurodegenerative disorders. In our patient, there was no personal or family history of cerebral degenerative disorders or specific previous and current pharmacological treatments other than antihypertensive drugs ramipril and amlodipine. Otherwise MRI revealed wide compression phenomena of subcortical structures and a significative shift of median line. The previously reported case of PS with no previous exposure to specific drugs was related to an iNPH in which brain asymmetry seems to affect neurotransmitters function by means of a downregulation of D2 receptors in the striatum due to nigrostriatal dopaminergic pathways alteration [
14,
20,
21]. In this case, a possible role of functional disruption of non-dopaminergic systems such as thalamo-cortical tract through the corona radiata may be hypotized. Experimental results suggest that axial posture impairment in PD are related to progressive loss of propioceptive integration during spatial orientation tasks despite the integrity of vestibular system [
22]. Some Authors suggested that an imbalance between control mechanisms of postural orientation and stabilization might explain both dystonic phenomena and instability in PD patients [
4,
19,
22]. In our case, tonic flexion of the trunk was indeed associated to left lateropulsion and static and dynamic postural instability suggesting such an impairment of sense of position and more generally a lateralized propioceptive dysfunction [
22]. Compressive effect of SDH on the afferent fibers to primary somatosensory cortex from ventral posterolateral nucleus of the thalamus may account for a subtle loss of the sense of position and movement and an impairment of proprioceptive integration resulting in an impairment of the control of body orientation [
16,
21]. Furthermore, a complex contribution of basal ganglia in postural control and body rotation may be postulated according to several lesion studies that accounted for uncontrolled axial posture after controlateral lesion of caudate and lenticular nucleus [
4,
18]. Displacement of subcortical structure in our patients may alter motor cortex connectivity to basal ganglia with consequent reduction of inhibition pathways to sensory-motor cortex because a particular involvement of unilateral caudate and lenticular nuclei [
4,
16,
22].