Positive and negative factors in movement control: a current review of Denny-Brown's hypothesis

Case Report: Catatonic Stupor in Behavioral Variant Frontotemporal Dementia

Catatonia is a psychomotor syndrome common to several medical and neuropsychiatric disorders. Here, we report on the case of a 95-year-old woman who underwent a radical change in personality characterized by sexual disinhibition, and physical and verbal aggressiveness. Over several months, she developed verbal stereotypies, gait deterioration, and double incontinence. She eventually developed mutism and an active opposition to all attempts to be fed or cared for. Benzodiazepines, olanzapine and electroconvulsive therapy were of no benefit. Magnetic resonance imaging revealed asymmetric (more severe on the right) frontotemporal, parietal, and upper brainstem atrophy. She died from sepsis without recovering from stupor seven years after the onset of symptoms. We believe that the initial behavioral disinhibition was related to the frontotemporal injury, whereas catatonic stupor reflected the progression of the degenerative process to the parietal cortices. Our case adds to the small number of cases of catatonia as a symptom of degenerative dementia. It also supports the idea that damage to the parietal cortex gives rise to pathological avoidance of which catatonic stupor represents an extreme form.

Laser-Evoked Vertex Potentials Predict Defensive Motor Actions

The vertex potential is the largest response that can be recorded in the electroencephalogram of an awake, healthy human. It is elicited by sudden and intense stimuli, and is composed by a negative–positive deflection. The stimulus properties that determine the vertex potential amplitude have been well characterized. Nonetheless, its functional significance remains elusive. The dominant interpretation is that it reflects neural activities related to the detection of salient stimuli. However, given that threatening stimuli elicit both vertex potentials and defensive movements, we hypothesized that the vertex potential is related to the execution of defensive actions. Here, we directly compared the salience and motoric interpretations by investigating the relationship between the amplitude of laser-evoked potentials (LEPs) and the response time of movements with different defensive values. First, we show that a larger LEP negative wave (N2 wave) predicts faster motor response times. Second, this prediction is significantly stronger when the motor response is defensive in nature. Third, the relation between the N2 wave and motor response time depends not only on the kinematic form of the movement, but also on whether that kinematic form serves as a functional defense of the body. Therefore, the N2 wave of the LEP encodes key defensive reactions to threats.

Alternating hemidystonia following traumatic brain injury as an unusual presentation of paroxysmal autonomic instability with dystonia syndrome

A 20-year-old man presented to the neurotrauma intensive care unit following blunt head injury. MRI revealed subarachnoid haemorrhage and multiple intraparenchymal haemorrhages suggesting severe brain injury. During recovery, the patient displayed intermittent episodes of alternating hemibody spasms with decerebrate/decorticate dystonic posturing. Episodes presented with autonomic dysregulation including hyperthermia, diaphoresis, tachypnoea, tachycardia and hypertension. Concern for seizure activity prompted simultaneous video monitoring and EEG testing. Results were without epileptiform activity suggesting against seizure as cause for alternating hemibody spasms. Paroxysmal autonomic instability with dystonia (PAID) was considered despite the unusual presentation. Intravenous hydromorphone was used for treatment, which relieved symptoms of autonomic dysregulation and dystonic posturing. PAID syndrome was diagnosed based on presentation with intermittent episodes of dystonia, autonomic dysregulation, absence of epileptiform activity and rapid response to opioid treatment. This case illustrates the clinical variability of this uncommon syndrome because alternating hemidystonia as main manifestation has not been previously described.

'An investigation of the nervous control of defecation' by Denny-Brown and Robertson: a classic paper revisited. 1935

In 1935 two young neurologists, Derek Denny-Brown and E. Graeme Robertson, published an article explaining the mechanisms underlying human defaecation based on a manometric study in patients with sacral root and spinal cord lesions, and normal subjects. This article is still routinely cited in studies of rectal and sphincter ani function. Unfortunately, however, the article itself is not written well, being composed of long convoluted sentences and containing 79 often indecipherable figures. Difficult-to-understand articles were common to the publications of Denny-Brown, who became one of the most prominent neurologists of the twentieth century. In accord with our prior work explaining Denny-Brown and Robertson's earlier paper on micturition, we provide here what we hope is a clear explanation of the methods and results in their study on defaecation.

Observations on the human rejection behaviour syndrome: Denny-Brown revisited

The parietal avoiding-rejection behaviour syndrome, first described by Denny-Brown in the rhesus monkey, has been reported only rarely in humans. Here, we describe a patient with rejection behaviour in the setting of progressive cognitive decline accompanied by cortical myoclonus.

Utilization behavior: clinical manifestations and neurological mechanisms

This paper describes a variety of motor release phenomena, including manual grasping and groping, imitation behavior, utilization behavior, and alien hand sign, their clinical manifestations. and proposed neural mechanisms. One of these specific neurobehavioral disorders, initially described by Lhermitte (Brain [1983] 106: 237-255), and termed utilization behavior, is addressed in more detail. Patients with this disorder are described as reaching out and using objects in the environment in an automatic manner. The current paper provides a comprehensive review of studies that have documented utilization behavior in individuals with a variety of pathologies, all having a specific predilection for the frontal lobes and frontal-striatal systems. Goldberg's (Behavioral and Brain Sciences [1985] 8: 567-616) theoretical framework for understanding motor release phenomena, which conceptualizes these behaviors as resulting from an imbalance between proposed medial (voluntary, goal directed, and future directed) and lateral (automatic, stimulus bound, and visually based) motor systems, is also discussed. Utilization behavior may prove to be a common underlying cause of high levels of excessive and intrusive motor behaviors within various clinical populations. A more comprehensive understanding of the neural systems underlying utilization behavior may prove highly useful for the differential diagnosis of conditions involving the mesial frontal cortex and fronto-striatal connections. Recent studies have started to investigate utilization behavior in clinical populations with known or suspected frontal system dysfunction, including adult patients with a variety of psychiatric conditions and children with ADHD.

Denny-Brown's views on the pathophysiology of dystonia

We review Denny-Brown's hypotheses on the mechanisms underlying motor behavior and his views on how dysfunction in these mechanisms can result in dystonia. His formulations were based upon clinical observations of patients with diseases of the central nervous system and on monkeys with surgically-induced lesions of structures affected by diseases in his patients. Denny-Brown viewed dystonia as resulting from an imbalance of reflex responses to natural stimulation, both tonically and phasically. The evidence for this view came from demonstration of alterations of dystonic postures by natural vestibular, cutaneous, proprioceptive and visual stimuli. His formulations remain highly useful to clinicians faced with a bewildering variety of postural and movement disorders.