Which of the following is not a cause of absent ankle jerks and up-going plantars?

Causes of absent ankle jerks and upgoing plantars is a common question as it implies both upper and lower motor neuron involvement. The more common single causes include cord compression involving both the cord (UMN) and nerve ganglia roots (LMN) as well as subacute combined degeneration of the cord. Other more common causes include the presence of more than one pathology, e.g. stroke (UMN) with superimposed peripheral neuropathy (LMN) — usually in a diabetic patient. In Friedrich’s ataxia, both cord and peripheral nerve involvement accompany cerebellar degeneration. These patients also have sensory loss, pescavus and may have complications such as diabetes and hypertrophic cardiomyopathy. Multiple sclerosis may cause a mixture of pyramidal signs (UMN), sensory loss (dorsal columns) and ataxia (cerebellum), but will never involve the LMN.