Lipomatosis of nerve (LN) is an intriguing pathological entity defined by the abundance of fibro-adipose tissue within the epineurium, a pathognomonic magnetic resonance imaging (MRI), and frequently associated nerve-territory overgrowth. A recent systematic review showed that the majority of cases are unilateral and predominately involve the median nerve. We reviewed bilateral cases of LN to further understand this pathology. We conducted a review of the literature and our institutional databases. The cases from the literature were sorted into three groups - bilaterally confirmed LN (n = 9), unilaterally confirmed, opposite side probable LN (n = 4), and probable bilateral LN (n = 10). Review of our institutional databases identified one case: a 47-year-old man. MRI revealed LN of the brachial plexus bilaterally. To our knowledge, this is the first reported case of brachial plexus LN occurring bilaterally. More research is necessary on this topic to further understand the genetic background of this entity, particularly in relationship to the overgrowth. (Journal of Surgical Orthopaedic Advances 30(1):044-049, 2021).

Department of Neurologic Surgery Mayo Clinic Rochester Minnesota

Department of Neurologic Surgery Mayo Clinic Rochester Minnesota; 1st Faculty of Medicine Charles University Prague Czech Republic

Department of Neurologic Surgery University of Utah Salt Lake City Utah

Department of Radiology Mayo Clinic Rochester Minnesota

Occult lipomatosis of the nerve as part of macrodystrophia lipomatosa: illustrative case