The aetiology of mirror writing: a new hypothesis.

Abstract

SUMMARY Twenty-eight cases of mirror writing were seen during a period of three and a half years. These consisted of 12 patients with essential tremor, nine with Parkinson's disease, three with spino-cerebellar degeneration and four other cases. There were no cases of hemiparesis, aphasia, apraxia, agnosia or confusion. Fragmentary reversals were excluded from this study. Since essential tremor, Parkinsonian tremor and cerebellar tremor can be abolished by a stereotaxic produce applied to the thalamus, a common neural pathway via the thalamic nuclei may exist in these disorders. The existence is therefore proposed of some neural mechanism that controls the higher cerebral function of writing via the thalamus. were unskilfully written and drawn because of his action tremor. When he was instructed to write with the left hand, however, he wrote kanji from right to left in mirror fashion without any hesitation. He did not even recognise his own mirror writing. In the case of the clock face, not only the numerals, but also the position of the clock digits were reversed. Prospective Evaluation of the Clinical Cases Following our discovery of this initial case, we decided to evaluate the incidence of mirror writing in cases of neurological disorders which included not only essential tremor, but also Parkinson's disease, spinocerebellar degeneration, cerebrovascular disease, and various other neurological complaints, on the basis of work in an outpatients clinic. In addition, 258 medical and nursing students were asked to cooperate by writing their names with both right and left hands without any further suggestions. Although these students were much younger than the patients and were therefore unsuitable as perfectly exact age and sex matched controls, they can nevertheless be used as examples of how normal subjects write with their left hands.The mirror writing we report on here was, of course, induced mirror writing, which is somewhat different from the many types of case with spontaneous mirror writing classified by Critchley. Yet in every case, mirror writing was demonstrated when our patients were instructed to write letters with their left hands.

Mirror writing and reversing single letters in stroke patients and normal elderly

“…This omission may have resulted in an underestimation of the prevalence of MW. Moreover, two cases have been reported [2,22] of left-hand MW following right hemisphere lesion. Yet, the performance of right-hemisphere damaged patients has been ignored in group studies.…”

“…We propose that the diagnosis of MW should be limited to the reversal of whole words, multi-digit numbers and full sentences, which reveal a disorder in coding the correct direction of writing rather than an inability to accomplish the correct spatial orientation of single letters. frequency of MW in an unselected series of hemiplegic patients varies between 2.4% [8] to 13% [22]. A higher frequency (24%) is reported when only patients with left hemisphere lesions were considered [23], however, none of the available studies on the frequency of mirror writing specifies the selection criteria of the sample [8,17,21,22].…”

Mirror writing in a patient with Alzheimer disease

“…Studies among the elderly in China and Japan have shown an increase in mirror writing in relation to cerebral damage and cognitive dysfunction [3,4]. A high prevalence of mirror writing has been described in patients with essential tremor, Parkinson disease, and cerebellar disorders [2].…”

“…Mirror writing may be transient or long lasting, and may affect single letters or characters, whole words or sentences. Although mirror writing occurs both spontaneously and pathologically, it is generally associated with cerebrovascular lesions in the dominant hemisphere [2].…”

The Role of External Cues in Korean Mirror Writing

“…The downwards writing observed in this patient implies that characteristics of mirror writing at the level of a connected script are language-specific [2,6,7] . The modern Korean script is typically written in the left-to-right direction, as are IndoEuropean scripts such as English.…”