Blink reflex in dyskinetic and nondyskinetic patients with Parkinson's disease

Eyelid Dysfunction in Neurodegenerative, Neurogenetic, and Neurometabolic Disease

Eye movement abnormalities are among the earliest clinical manifestations of inherited and acquired neurodegenerative diseases and play an integral role in their diagnosis. Eyelid movement is neuroanatomically linked to eye movement, and thus eyelid dysfunction can also be a distinguishing feature of neurodegenerative disease and complements eye movement abnormalities in helping us to understand their pathophysiology. In this review, we summarize the various eyelid abnormalities that can occur in neurodegenerative, neurogenetic, and neurometabolic diseases. We discuss eyelid disorders, such as ptosis, eyelid retraction, abnormal spontaneous and reflexive blinking, blepharospasm, and eyelid apraxia in the context of the neuroanatomic pathways that are affected. We also review the literature regarding the prevalence of eyelid abnormalities in different neurologic diseases as well as treatment strategies (Table 1).

Specific brainstem and cortico-spinal reflex abnormalities in coexisting essential tremor and Parkinson's disease (ET-PD)

OBJECTIVE

We aimed to analyze functional changes at brainstem and spinal levels in essential tremor (ET), Parkinson's disease (PD) and coexisting essential tremor and Parkinson's disease (ET-PD).

PATIENTS AND METHOD

Age- and gender-matched patients with tremor (15 ET, 7 ET with resting tremor, 25 ET-PD and 10 PD) and 12 healthy subjects were enrolled in the study. Diagnosis was established according to standardized clinical criteria. Electrophysiological studies included blink reflex (BR), auditory startle reaction (ASR) and long latency reflex (LLR).

RESULTS

Blink reflex was normal and similar in all groups. Probability of ASR was significantly lower in ET-PD group whereas it was similar to healthy subjects in ET and PD (P<0.001). LLR was recorded during voluntary activity in all three groups. LLR II was more common in ET, PD and ET-PD groups. LLR III was far more common in the PD group (n=3, 13.6% in ET; n=4, 16.0% in ET-PD and n=7, 46.7% in PD; p=0.037).

CONCLUSIONS

Despite the integrity of BR pathways, ASR and LLR show distinctive abnormalities in ET-PD. In our opinion, our electrophysiological findings support the hypothesis that ET-PD is a distinct entity.

Abnormalities in long latency responses to superior laryngeal nerve stimulation in adductor spasmodic dysphonia

Sensorimotor responses to repeated electrical stimulation of the superior laryngeal nerve were compared in 8 patients with adductor spasmodic dysphonia (ADSD) and 11 normal controls to determine if adductor response disinhibition occurred in ADSD. Pairs of electrical pulses were presented at interstimulus intervals varying from 100 to 5,000 milliseconds (ms). Three responses were measured in thyroarytenoid muscles: ipsilateral R1 responses at 17 ms and ipsilateral and contralateral R2 responses between 60 and 75 ms. Conditioned response characteristics, the percent occurrence and percentage amplitude of initial responses, were measures of response inhibition. As a group, the patients had reduced response inhibition: their conditioned ipsilateral R1 response amplitudes were increased, as was the frequency of their conditioned contralateral muscle responses (p < or = .002) compared to normal. However, the patients' initial responses were normal in latency and frequency characteristics, demonstrating that the brain stem mechanisms for these responses were intact. These results suggest a central disinhibition of laryngeal responses to sensory input in ADSD.

Primitive reflexes in Alzheimer's disease and vascular dementia

Data on the prevalence and clinical value of primitive reflexes (PRs) in dementia are controversial, mainly due to a lack of standardization of the methods by which these signs are elicited and scored. A standardized protocol was used to investigate eight PRs in 20 patients with Alzheimer's disease (AD), 20 patients with vascular dementia (VD), and 20 control subjects for each group. Both patient groups showed considerably more PRs than the control groups. The prevalence of PRs was related to the severity of dementia. No single reflex or combination of PR pathognomonic for dementia could be distinguished. The PR profile of AD and VD patients were similar.

Primitive reflexes in Parkinson's disease

A standardised protocol for the examination of 15 primitive reflexes in which the amplitude and the persistence were scored separately, was applied to 25 patients with Parkinson's disease and an equal number of healthy matched control subjects. Most reflexes were found considerably more often in the patients than in the control subjects, especially the snout, the glabellar tap, and its variant, the nasopalpebral reflex. Only the mouth open finger spread reflex was present more often in the control subjects. For all reflexes except this last, the scores for amplitude and persistence of the reflexes for the control group never exceeded the scores for the patient group. Reflexes persisted more often in the patients than in the control subjects. Parkinsonism alone can explain a large number of primitive reflexes, irrespective of the severity or duration of the disease. In contrast, the number of reflexes was related more closely to cognitive scales. It is concluded that such reflexes may be helpful in diagnosing Parkinson's disease. In addition, a standardised protocol for eliciting and scoring is essential for the study of these reflexes in parkinsonism and other neuropsychiatric conditions.

Primitive reflexes in healthy, adult volunteers and neurological patients: methodological issues

A study was made to determine whether two experienced clinicians elicited and scored primitive reflexes (PR) differently and whether reliability could be improved by standardization. Three studies were carried out, using a protocol for the examination of 14 PR. In the first study with 31 healthy young subjects, two investigators found virtually no difference in the routine neurological examination. However, the interobserver agreement was very poor, indicating the need for a further improvement of the PR protocol. In the second study, 30 neurological patients were examined with an improved, more explicit and standardized protocol, in which the amplitude and the persistence of the reflex were scored separately. Interobserver agreement improved considerably, and was high for amplitude as well as persistence. In the third study, 36 neurological patients were examined twice by one investigator within 2 weeks. Good to excellent intraobserver agreement was found. No pathognomonic or strictly localizing reflex could be distinguished.

A correlation study between blink reflex habituation and clinical state in patients with Parkinson's disease

The neurologic states and activities of daily life of patients with Parkinson's disease were evaluated using a rating scale with subitems, and subsequently the neurologic disturbance scores and the daily activity impairment scores were obtained. Subjects consisted of 19 normal controls, and 55 ambulatory patients without marked dyskinesia who were on various anti-parkinsonian drugs. Blink reflex was elicited by paired electrical stimulation over the supraorbital nerve. The interval time between the conditioning stimulation and the test stimulation was set at 200 ms, and 5 serial ipsilateral maximal R2 amplitudes on the stimulated side were measured. The mean of the paired maximal R2 amplitude ratio (test/conditioning), expressed as a percentage, was defined as the habituation index. The habituation indices in normal controls and those with Parkinson's disease were 17.1 +/- 7.6 and 51.9 +/- 29.3, respectively (P less than 0.01). The degree of akinesia, rigidity, balance/gait and dysarthria was positively correlated with the habituation index (P less than 0.01), while tremor was not. On the whole the habituation index was found to have a significant correlation not only with the neurologic disturbance score but also with the daily activity impairment score (P less than 0.01).